Metal-mediated base pairs in parallel-stranded DNA

• Jens Müller

Beilstein J. Org. Chem. 2017, 13, 2671–2681, doi:10.3762/bjoc.13.265

• in the context of this review is the pyrimidine:purine:pyrimidine triplex, where each base triple formally comprises a regular Watson–Crick base pair and an additional pyrimidine residue hydrogen-bonded to the central purine moiety via its Hoogsteen edge. Conceptually, this Hoogsteen-bonded part of

• glycosidic bond conformations [46]. It needs to be noted that these correlations are derived from base pairs and triples comprising canonical purine and pyrimidine nucleobases only. In particular, it is assumed that both Hoogsteen and reversed Hoogsteen pairing involve the Hoogsteen edge of one purine

• residue and the Watson–Crick edge of the complementary pyrimidine or purine moiety. Artificial base pairs involving two purine entities facing each other via their respective Hoogsteen edge (vide infra, Scheme 8b) need to be treated differently, as this additional structural change leads to a change from

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• preparation of acid 3 homologues (with a methylene linker between the carboxylic group and the pyrimidine ring) and their isomers resulting from two alternative regioselective pathways for the decarboxylative nucleophilic addition of malonic acid and its mono(thio)esters. Results and Discussion We first

• (1a) to substituted pyrimidones 2b–e carried out in the presence of TEA in toluene for 8 h has shown that a substituent at position 1 of the pyrimidine ring can significantly influence the progress of the reaction (Table 4). Thus, N1-alkyl-substituted compounds 2b–e exhibited a lower reactivity

• be increased by introduction of the ester functionality at position 5 as well as allyl, various benzyl or phenyl substituents at position 1 of the pyrimidine core. Notably, esters 6 and thioesters 8 are remarkable for their potential application as smooth amine acylating agents. It has been shown

¹⁵N-Labelling and structure determination of adamantylated azolo-azines in solution

• Sergey L. Deev,
• Alexander S. Paramonov,
• Tatyana S. Shestakova,
• Igor A. Khalymbadzha,
• Oleg N. Chupakhin,
• Julia O. Subbotina,
• Oleg S. Eltsov,
• Pavel A. Slepukhin,
• Vladimir L. Rusinov,
• Alexander S. Arseniev and
• Zakhar O. Shenkarev

Beilstein J. Org. Chem. 2017, 13, 2535–2548, doi:10.3762/bjoc.13.250

• constants for the structure determinations of N-alkylated nitrogen-containing heterocycles in solution. This method was tested on the N-adamantylated products in a series of azolo-1,2,4-triazines and 1,2,4-triazolo[1,5-a]pyrimidine. The syntheses of adamantylated azolo-azines were based on the interactions

• -triazolo[1,5-a]pyrimidine [30], 1,2,4-triazolo[5,1-c][1,2,4]triazinone [31] and tetrazolo[1,5-b][1,2,4]triazinone [32] can be obtained by the fusion of an azine ring to an azole fragment. This method can be used for the selective incorporation of 15N atoms in different azolo-azines. Recently, we tested

• complicated the subsequent NMR analysis. Meanwhile, the application of [2,3-15N2]-5-aminotetrazole 7-15N2 provided the single double-labelled products in the tetrazolo[1,5-a]pyrimidine series [33]. Thus, in the current work, [2,3-15N2]-5-aminotetrazole 7-15N2 (98% enrichment for each of the labelled 15N atoms

Synthesis, effect of substituents on the regiochemistry and equilibrium studies of tetrazolo[1,5-a]pyrimidine/2-azidopyrimidines

• Elisandra Scapin,
• Paulo R. S. Salbego,
• Caroline R. Bender,
• Alexandre R. Meyer,
• Anderson B. Pagliari,
• Tainára Orlando,
• Geórgia C. Zimmer,
• Clarissa P. Frizzo,
• Helio G. Bonacorso,
• Nilo Zanatta and
• Marcos A. P. Martins

Beilstein J. Org. Chem. 2017, 13, 2396–2407, doi:10.3762/bjoc.13.237

• theory (DFT) for energetic and molecular orbital (MO) calculations. Keywords: 5-aminotetrazol; azide–tetrazole equilibrium; 2-azidopyrimidine; β-enaminones; tetrazolo[1,5-a]pyrimidine; trifluoromethylatedtetrazolo[1,5-a]pyrimidines; Introduction Tetrazolo[1,5-a]pyrimidines have attracted attention in

• using ultrasound irradiation promoted shorter reaction times, high regioselectivity, and excellent yields, when compared with conventional thermal heating [30]. Presently, we demonstrate an eco-friendly synthesis of 5- and 7-substituted tetrazolo[1,5-a]pyrimidine isomers, in good to excellent yields

• the β-enaminone precursor and (iii) elucidate the azide–tetrazole equilibrium when the compound is in solid form or dissolved in distinct solvents. The tetrazolo[1,5-a]pyrimidine synthesis was conducted from a cyclocondensation reaction of the type [CCC + NCN], in which the CCC block is a series of β

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• demonstrate the regiochemistry of the reaction. These cascade reactions proceed first through a Michael addition of the primary amine on the enone, followed by an intramolecular cyclization by the pyridine/pyrimidine nucleus. Unfortunately, no crystal structure could be obtained for the imidazopyrimidines and

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• scale-up process, where the key reaction, a Zeigler coupling, of an early trifluoromethylimidazole intermediate 100 with commercially available 2-chloro-5-fluoropyrimidine afforded 101 (a compound with partially saturated pyrimidine framework). An aerobic oxidative dehydrogenation of 101 in the presence

• of molecular oxygen and with catalytic copper acetate (Cu(OAc)2) generated the desired pyrimidine 102 which was converted to the final products in a few more steps. This is one of the noteworthy examples where oxidative dehydrogenation has been utilized for the synthesis of a key intermediate of an

New electroactive asymmetrical chalcones and therefrom derived 2-amino- / 2-(1H-pyrrol-1-yl)pyrimidines, containing an N-[ω-(4-methoxyphenoxy)alkyl]carbazole fragment: synthesis, optical and electrochemical properties

• Daria G. Selivanova,
• Alexei A. Gorbunov,
• Olga A. Mayorova,
• Alexander N. Vasyanin,
• Igor V. Lunegov,
• Elena V. Shklyaeva and
• Georgii G. Abashev

Beilstein J. Org. Chem. 2017, 13, 1583–1595, doi:10.3762/bjoc.13.158

• ; electrochemical oxidation; pyrimidine; solvatochromism; Introduction Nowadays a great number of research projects concerning the synthesis of organic conjugated systems with a wide scope of their applications, primarily as materials for organic electronic devices such as light-emitting diodes, field-effect

• structure of side chains [10]. In this paper we describe a synthetic approach to some new D–π–A–D conjugated systems which include 9-[ω-(4-methoxyphenoxy)alkyl]carbazole as a donor fragment (D) and prop-2-enone and pyrimidine units as electron acceptor moieties (A). The optical and electrochemical

• linked with a central pyrimidine core and another one is linked by a rigid thiophene cycle as a π-conjugated bridge. We have applied a usual synthetic protocol which includes eight successive steps: O-alkylation of 4-methoxyphenol (1), N-alkylation of carbazole (2), formylation or acetylation of a

Strategies toward protecting group-free glycosylation through selective activation of the anomeric center

• A. Michael Downey and
• Michal Hocek

Beilstein J. Org. Chem. 2017, 13, 1239–1279, doi:10.3762/bjoc.13.123

• synthesis of modified pyrimidine nucleosides using E. coli NPs [26]. 2.2 Synthetic strategies The classical protecting-group-free (pre-2000) synthetic strategies are dated back to well over 100 years with the discovery of the Fischer glycosylation (Scheme 6) [27][28]. Methanol can be glycosylated with D

From chemical metabolism to life: the origin of the genetic coding process

• Antoine Danchin

Beilstein J. Org. Chem. 2017, 13, 1119–1135, doi:10.3762/bjoc.13.111

• convincing way [31]. Other coenzymes, possibly generated by such a swinging-arm thioester-dependent catalysis, may have been precursors of nucleotides, the essential building blocks of nucleic acids. As a matter of fact, extant biosynthesis of nucleotides (built on purine and pyrimidine carbon–nitrogen

• aromatic heterocycles) is based on the incorporation of amino acids in the core of nucleotide precursors. Pyrimidine nucleotide biosynthesis uses aspartate and combines together ubiquitous molecules, water, carbon dioxide, ammonium and phosphate (forming carbamoyl phosphate, also a precursor of arginine

Nucleophilic displacement reactions of 5′-derivatised nucleosides in a vibration ball mill

• Olga Eguaogie,
• Patrick F. Conlon,
• Francesco Ravalico,
• Jamie S. T. Sweet,
• Thomas B. Elder,
• Louis P. Conway,
• Marc E. Lennon,
• David R. W. Hodgson and
• Joseph S. Vyle

Beilstein J. Org. Chem. 2017, 13, 87–92, doi:10.3762/bjoc.13.11

• reactions require the use of high-boiling, dipolar aprotic solvents and anionic nucleophiles under anhydrous conditions at elevated temperatures (up to 150 °C). Competing intramolecular cyclisation reactions between both purine and pyrimidine nucleobases and (especially) the 5′-position of the (deoxy

• were observed with IdT (1d) and IdG (1e) although maximal conversion of IdG was achieved within one hour in the absence of added liquid (the reaction was inhibited in the presence of DMF). During these studies, LAG of both purine and pyrimidine substrates in the presence of ethyl acetate or hexane was

Enzymatic synthesis and phosphorolysis of 4(2)-thioxo- and 6(5)-azapyrimidine nucleosides by E. coli nucleoside phosphorylases

• Vladimir A. Stepchenko,
• Anatoly I. Miroshnikov,
• Frank Seela and
• Igor A. Mikhailopulo

Beilstein J. Org. Chem. 2016, 12, 2588–2601, doi:10.3762/bjoc.12.254

• comparison with the natural pyrimidine nucleosides in order to understand the impact of such modifications as monomers or constituents of oligonucleotides [8][9][10][11][12][13][14]. Thioxopyrimidine nucleosides as such, as well as building blocks of artificial oligonucleotides demonstrate promising

• antiviral activity in various experiments [15][16][17][18][19][20][21][22]. Regarding the chemical synthesis of this class of pyrimidine nucleosides various approaches were published (see, e.g., [8][9][10][11][14][15][16][23][24]; reviewed by Vorbrüggen and Ruh-Pohlenz [25]). On the contrary, only few

• 2.4.2.4) phosphorylases [36], and (ii) the role of structural features and electronic properties of the pyrimidine bases and nucleosides in the recognition by E. coli nucleoside phosphorylases. Results and Discussion Thioxo- and 6-aza-pyrimidines used in the transglycosylation reaction with recombinant E

A new paradigm for designing ring construction strategies for green organic synthesis: implications for the discovery of multicomponent reactions to build molecules containing a single ring

• John Andraos

Beilstein J. Org. Chem. 2016, 12, 2420–2442, doi:10.3762/bjoc.12.236

• dihydropyridine, hydantoin, imidazole, indole, isoquinoline, isoxazole, oxazole, 4H-pyran, pyrazine, pyridazine, pyridine, pyridinone, pyrimidine, pyrimidone, pyrrole, 3H-quinazolin-4-one, quinoline, 1H-quinolin-4-one, and thiophene. For heterocycles that are composed of a fused aromatic ring, such as

Methylpalladium complexes with pyrimidine-functionalized N-heterocyclic carbene ligands

• Dirk Meyer and
• Thomas Strassner

Beilstein J. Org. Chem. 2016, 12, 1557–1565, doi:10.3762/bjoc.12.150

• Dirk Meyer Thomas Strassner Physikalische Organische Chemie, TU Dresden, Bergstraße 66, 01062 Dresden, Germany 10.3762/bjoc.12.150 Abstract A series of methylpalladium(II) complexes with pyrimidine-NHC ligands carrying different aryl- and alkyl substituents R ([((pym)^(NHC-R))PdII(CH3)X] with X

• -NHC ligand [33]. To study the differences between both systems we synthesized palladium [34] and platinum [35] “hybrid complexes” with ligands combining both structural elements the pyrimidine as well as the NHC fragment. We also used density functional theory (DFT) calculations to investigate the

• different donor character. The experimentally determined geometrical parameters are in good agreement with the computed results. Interestingly, complexes 9, 10 and 12 show only one discrete doublet for the m-pyrimidine proton signals in the 1H NMR spectrum in DMSO-d6 indicating that the pyrimidine ring

Synthesis of highly functionalized 2,2'-bipyridines by cyclocondensation of β-ketoenamides – scope and limitations

• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1170–1177, doi:10.3762/bjoc.12.112

• alkoxyallene [46][47]. As mentioned above β-ketoenamide 3i is a good precursor for 2,2´-bipyridine derivative 4i, but Scheme 4 also reveals that this intermediate could be converted into the expected pyrimidine derivative 7 by treatment with ammonium acetate [48][49][50] or into pyrimidine N-oxide 8 by

• methoxylation of compound 3a we unexpectedly observed the formation of the 5-acetyl-substituted oxazole derivative 6. However, precursor 3i was smoothly available from acetylacetone 1a. It could smoothly be transformed into the desired bipyridine derivative 4i, but also into the related pyrimidine and

• pyrimidine N-oxide derivatives 7 and 8. Altogether, we could confirm that our approach to functionalized pyridine derivatives by cyclocondensation of β-ketoenamides is also a very versatile and flexible method for the synthesis of unsymmetrically substituted bipyridine derivatives or related heterocyclic

Modular synthesis of the pyrimidine core of the manzacidins by divergent Tsuji–Trost coupling

• Sebastian Bretzke,
• Stephan Scheeff,
• Felicitas Vollmeyer,
• Friederike Eberhagen,
• Frank Rominger and
• Dirk Menche

Beilstein J. Org. Chem. 2016, 12, 1111–1121, doi:10.3762/bjoc.12.107

• -metathesis of a challenging homoallylic urea substrate, which proceeds in good yields in the presence of an organic phosphoric acid. Keywords: cross-metathesis; natural products; pyrimidines; Tsuji–Trost reaction; synthetic methods; Introduction Chiral pyrimidine motifs constitute prevalent structural

• allylic substitution reaction of a joint precursor 5. Subsequently this strategy is successfully applied to the synthesis of the authentic pyrimidine cores 3 and 4 of manzacidin A (1) and ent-manzacidin C (2). Results and Discussion General synthetic concept As part of our ongoing efforts to the design of

The role of alkyl substituents in deazaadenine-based diarylethene photoswitches

• Christopher Sarter,
• Michael Heimes and
• Andres Jäschke

Beilstein J. Org. Chem. 2016, 12, 1103–1110, doi:10.3762/bjoc.12.106

• -based photoswitchable nucleosides. The design of these molecules challenged two of the established design rules for diarylethene-based photoswitches (Figure 1C) [45]: (1) They incorporated a six-membered pyrimidine ring, and (2) – more importantly – only one methyl group, rather than two, was present at

• are compared. Therefore, we set out to clarify this matter. If pyrimidine-based diarylethenes with one methyl group are good photoswitches, purine derivatives might work as well with just one methyl group. If this hypothesis was true, the synthesis of such photoswitches would be much simplified

• diarylethenes by direct comparison, and ii) we wanted to test whether our prior successful violation of this “rule” with photochromic pyrimidine nucleosides could be expanded to purine nucleosides. Our analysis reveals that – depending on the substituents – the one-methyl 7-deaza-2’-deoxyadenosine compounds can

Bi- and trinuclear copper(I) complexes of 1,2,3-triazole-tethered NHC ligands: synthesis, structure, and catalytic properties

• Shaojin Gu,
• Jiehao Du,
• Jingjing Huang,
• Huan Xia,
• Ling Yang,
• Weilin Xu and
• Chunxin Lu

Beilstein J. Org. Chem. 2016, 12, 863–873, doi:10.3762/bjoc.12.85

• [1][2][3][4][5][6][7][8][9][10][11][12]. A number of transition metal complexes of NHCs containing pyridine [13], pyrimidine [14], pyrazole [15][16], naphthyridine [17], pyridazine [18], and phenanthroline [19][20] donating groups have been studied in metal-catalyzed organic transformations. Recently

• excess of copper powder in CH3CN at 50 °C for 5 h. As shown in Scheme 1, reactions of the pyrimidine imidazolium salt 1a with copper powder in acetonitrile afforded a light yellow Cu(II) complex. In complex 2, the carbenic carbon atom was oxidized into carbonyl, which is similar with the reported

• two L2 ligands. The two ligands are arranged in head-to-tail manner. The copper ions are each tri-coordinated by one carbene carbon atom, one nitrogen from pyrimidine, and one nitrogen atom of the triazole rings from two different L2 ligands. The Cu–carbene bond distances are 1.896(6) and 1.899(5) Å

Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

• Vito Rizzi,
• Sergio Matera,
• Paola Semeraro,
• Paola Fini and
• Pinalysa Cosma

Beilstein J. Org. Chem. 2016, 12, 549–563, doi:10.3762/bjoc.12.54

• presence of CDs to prevent its degradation under irradiation. UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion

• related to a π–π* transition into the second lowest excited singlet (S2) state of the molecule. As a result, the delocalized electrons on the pyrimidine ring were supposed to be involved in a transition having a charge transfer character [26]. Taking this into account and with the prospect of an

• through a re-organization of solvating water molecules. Undoubtedly, a combination of these two effects could be considered. At this point, since the obtained UV–vis results are not sufficiently clear to definitely prove the formation of S4TdR/CDs inclusion complexes, in which the pyrimidine ring is

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• results, the high association constant observed with γ-CD is mainly due to a good fitting of the pyrimidine ring into the cavity, while one ethoxy substituent protruding from the lower rim. In the cases of α- and β-CD, the phosphoryl residue is located outside the cavity. For α- and β-CD, the methyl

Base metal-catalyzed benzylic oxidation of (aryl)(heteroaryl)methanes with molecular oxygen

• Hans Sterckx,
• Johan De Houwer,
• Carl Mensch,
• Wouter Herrebout,
• Kourosch Abbaspour Tehrani and
• Bert U. W. Maes

Beilstein J. Org. Chem. 2016, 12, 144–153, doi:10.3762/bjoc.12.16

• these more challenging substrates. Interestingly, phenyl(quinolin-2-yl)methanone (6a) and phenyl(quinolin-4-yl)methanone (6b) were formed in moderate yields indicating that larger aromatic systems are compatible with the reaction conditions. In the case of 2-(4-chlorobenzyl)pyrimidine (5c) the standard

• ) could be obtained in 92% yield. In contrast to the two former cases, 4-(4-chlorobenzyl)pyrimidine (5e) could neither be oxidized at 100 °C nor at 130 °C. Competitive C–H activation of the 2 position is presumed to be the reason for this observation. Blocking this position by a methyl group (5f

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• analog 26) showed high selectivity in binding pyrimidine mismatches [48]. The affinity of 26 for a TT mismatch in DNA was sufficient to inhibit the binding M. TaqI and, thus, potentially interfere with mismatch repair enzymes that have been implicated in certain diseases [49]. In 2009, Brent Iverson and

Recent advances in copper-catalyzed C–H bond amidation

• Jie-Ping Wan and
• Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

• heterocycle, the pyrimidine ring was disclosed as useful DG in copper-catalyzed C–H activation. As reported by Shen and co-workers [60], the C–H bond in indoles 47 and benzenes 48 could be effectively activated with copper in the presence of DGs such as pyrimidin-2-yl, pyridine-2-yl or benzoyl to provide

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines

• Mingxing Liu,
• Jiarong Li,
• Hongxin Chai,
• Kai Zhang,
• Deli Yang,
• Qi Zhang and
• Daxin Shi

Beilstein J. Org. Chem. 2015, 11, 2125–2131, doi:10.3762/bjoc.11.229

• Mingxing Liu Jiarong Li Hongxin Chai Kai Zhang Deli Yang Qi Zhang Daxin Shi School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing, 100081, China 10.3762/bjoc.11.229 Abstract An efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidine derivatives by the four

• -6-(2-nitrophenyl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine was determined by single crystal X-ray diffraction. Keywords: four-component; one-pot; pyrazolo[3,4-d]pyrimidine; sodium alkoxide; Introduction Heterocycles containing a pyrimidine ring are extensively present in natural products and are very

• catalyst (Table 1, entries 1 and 2). Sodium hydroxide could catalyze this reaction, but pyrazolo[3,4-d]pyrimidinone 5aa was obtained instead of pyrazolo[3,4-d]pyrimidine 5a (Table 1, entry 3). This shows that the catalytic properties of sodium hydroxide have some limitations. Fortunately, some strong bases

Synthesis and structures of ruthenium–NHC complexes and their catalysis in hydrogen transfer reaction

• Chao Chen,
• Chunxin Lu,
• Qing Zheng,
• Shengliang Ni,
• Min Zhang and
• Wanzhi Chen

Beilstein J. Org. Chem. 2015, 11, 1786–1795, doi:10.3762/bjoc.11.194

• , China 10.3762/bjoc.11.194 Abstract Ruthenium complexes [Ru(L1)2(CH3CN)2](PF6)2 (1), [RuL1(CH3CN)4](PF6)2 (2) and [RuL2(CH3CN)3](PF6)2 (3) (L1= 3-methyl-1-(pyrimidine-2-yl)imidazolylidene, L2 = 1,3-bis(pyridin-2-ylmethyl)benzimidazolylidene) were obtained through a transmetallation reaction of the

• corresponding nickel–NHC complexes with [Ru(p-cymene)2Cl2]2 in refluxing acetonitrile solution. The crystal structures of three complexes determined by X-ray analyses show that the central Ru(II) atoms are coordinated by pyrimidine- or pyridine-functionalized N-heterocyclic carbene and acetonitrile ligands

• ]. In continuation of our studies on functionalized Ru(II)–NHC complexes containing acetonitrile ligands, we herein report the synthesis and characterization of three pyrimidine- and pyridine-functionalized NHC–ruthenium complexes containing two, four, and three acetonitrile ligands, respectively. These

Indolizines and pyrrolo[1,2-c]pyrimidines decorated with a pyrimidine and a pyridine unit respectively

• Marcel Mirel Popa,
• Emilian Georgescu,
• Mino R. Caira,
• Florentina Georgescu,
• Constantin Draghici,
• Raluca Stan,
• Calin Deleanu and
• Florea Dumitrascu

Beilstein J. Org. Chem. 2015, 11, 1079–1088, doi:10.3762/bjoc.11.121

• Fundulea, Calarasi, Romania 10.3762/bjoc.11.121 Abstract The three possible structural isomers of 4-(pyridyl)pyrimidine were employed for the synthesis of new pyrrolo[1,2-c]pyrimidines and new indolizines, by 1,3-dipolar cycloaddition reaction of their corresponding N-ylides generated in situ from their

• corresponding cycloimmonium bromides. In the case of 4-(3-pyridyl)pyrimidine and 4-(4-pyridyl)pyrimidine the quaternization reactions occur as expected at the pyridine nitrogen atom leading to pyridinium bromides and consequently to new indolizines via the corresponding pyridinium N-ylides. However, in the case

• of 4-(2-pyridyl)pyrimidine the steric hindrance directs the reaction to the pyrimidinium N-ylides and, subsequently, to the formation of the pyrrolo[1,2-c]pyrimidines. The new pyrrolo[1,2-c]pyrimidines and the new indolizines were structurally characterized through NMR spectroscopy. The X-ray