Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• reactivity analogous to aldonitrones, which enables their conversion via [3 + 2]-cycloadditions with dipolarophiles such as activated ethylenes [8][9], activated acetylenes [10][11] or isocyanates [11][12]. The initially formed [3 + 2]-cycloadducts undergo spontaneous secondary conversions leading to re

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• generate the reactive species by dehydration of carbamates under mild conditions and the ultimate formation of isocyanates which can be derivatized in situ [54]. The conditions were optimized with alcohol 25 substituted by a 2-phenylethyl group at the oxygen-bearing carbon atom (C4) and possessing gem

• subsequently added to the reaction mixture. Under these conditions, the corresponding trifluoroacetamides 51–54 could be effectively isolated in good yields (73–85%). The addition of pyridine to the isocyanates J arising from the [3,3]-sigmatropic rearrangement would probably generate the zwitterionic

Gold-catalyzed post-Ugi alkyne hydroarylation for the synthesis of 2-quinolones

• Xiaochen Du,
• Jianjun Huang,
• Anton A. Nechaev,
• Ruwei Yao,
• Jing Gong,
• Erik V. Van der Eycken,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2018, 14, 2572–2579, doi:10.3762/bjoc.14.234

• -deficient aromatic aldehydes only low yields were achieved during the Ugi step. Yet, the subsequent gold-catalyzed cyclization worked well delivering the 2-quinolones 8f–h in up to 93% yield. Besides, several aliphatic and aromatic isocyanates 5 have been successfully employed for the preparation of 2

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• alkenes, which required a stoichiometric amount of oxidant. Herein, we wish to review the cobalt-catalyzed hydroarylation of alkynes, alkenes, allenes, enynes, imines, and isocyanates. These reactions usually proceed via either an oxidative addition of Ar–H to a low-valent cobalt to form A1 intermediate

• -catalyzed hydroarylation of C=X bonds Transition-metal-catalyzed addition of C–H bond to polar π bonds such as imines, isocyanates and carbonyls is one of the efficient methods to incorporate heteroatoms in organic molecules [45]. Yoshikai et al. developed an addition reaction of arylpyridines 3 to imines

• of aromatic, vinyl, and heterocyclic amides. Thus, Ackermann and co-workers developed an inexpensive cobalt-catalyzed hydroarylation of isocyanates with (hetero)arenes 64 (Scheme 41) [100]. The reaction can tolerate a broad range of arenes and isocyanates, providing amide products 65 with notable

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• electrophiles such as epichlorohydrin [6], organic carbonates [7][8][9] or bis-isocyanates [10], in variable ratios depending on the required degree of reticulation. The process, of course, exploits the nucleophilic reactivity of the hydroxy groups of the macrocycle oligosaccharide unit. In general, CyNSs

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• , urethanes and isocyanates point inward (Scheme 9). This observation was confirmed by X-ray crystallography as well as calculations at the B3LYP/6-31G** level [38][39]. The tert-butyl groups provide steric protection to the exo sides of the molecules, making the diisocyanate stable at ordinary temperatures

Diosgenyl 2-amino-2-deoxy-β-D-galactopyranoside: synthesis, derivatives and antimicrobial activity

• Henryk Myszka,
• Patrycja Sokołowska,
• Agnieszka Cieślińska,
• Andrzej Nowacki,
• Maciej Jaśkiewicz,
• Wojciech Kamysz and
• Beata Liberek

Beilstein J. Org. Chem. 2017, 13, 2310–2315, doi:10.3762/bjoc.13.227

• the condensation of saccharides with ureas or the reaction of glycosylamines, amino sugar, or aminoglycosides with isocyanates, or their equivalents such as carbamates [32][33]. Ureido saponins presented here were obtained in the reaction of ethyl isocyanate (8), chloroethyl isocyanate (9) and phenyl

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• reactive in the amination reaction. Ureas Just as thioureas are typically synthesized by coupling reaction between amines and isothiocyanates, ureas as oxygen analogues are prepared from the corresponding isocyanates. This approach was employed in the synthesis of anion binding 1-(pyridin-3-yl)-3-p

• more nucleophilic in the addition reaction to isocyanates (Scheme 15a). The ability to selectively convert o-pda into non-symmetrical mono-thioureas provided an opportunity to synthesize hybrid urea–thiourea derivatives 37a–d in a one-pot, two-step mechanochemical solvent-free process. After ball

• ). Sulfonylureas could also be obtained by coupling of sulfonyl isocyanates with amines which was demonstrated by an efficient solvent-, base- and catalyst-free synthesis of tolbutamide (93%) starting from p-toluenesulfonyl isocyanate and n-butylamine. However, this approach was not further pursued due to the air

Regioselective (thio)carbamoylation of 2,7-di-tert-butylpyrene at the 1-position with iso(thio)cyanates

• Anna Wrona-Piotrowicz,
• Marzena Witalewska,
• Janusz Zakrzewski and
• Anna Makal

Beilstein J. Org. Chem. 2017, 13, 1032–1038, doi:10.3762/bjoc.13.102

• photophysical properties [4][10][13][14][15][16][17][18][19][20], we thought it would be of interest to study its reactivity in the above reaction (and to extend its scope for isocyanates). An additional reason for such a study was the fact that thioamides (and amides) are versatile starting materials in the

• syntheses of various products (especially heterocycles) [21][22]. Furthermore, aromatic amides undergo a variety of directed C–H bond functionalizations [23]. Herein we report that the reaction of 2 with aliphatic isocyanates and isothiocyanates proceeds regioselectively at the 1-position (Scheme 1

• ). Results and Discussion The reaction was carried out at room temperature in dichloromethane using 1.7 equiv of isocyanate or isothiocyanate and 3.3 equiv of TfOH. For the isocyanates, the reaction was completed in less than 5 min, whereas the reaction with isothiocyanates required ≈30 min for completion

Isoxazole derivatives as new nitric oxide elicitors in plants

• Anca Oancea,
• Emilian Georgescu,
• Florentina Georgescu,
• Alina Nicolescu,
• Elena Iulia Oprita,
• Catalina Tudora,
• Lucian Vladulescu,
• Marius-Constantin Vladulescu,
• Florin Oancea and
• Calin Deleanu

Beilstein J. Org. Chem. 2017, 13, 659–664, doi:10.3762/bjoc.13.65

• compounds with isocyanates in the presence of tertiary alkylamines [33]. Generally, the cycloaddition reactions of nitrile oxides to alkenes yield isoxazolines or a mixture of isoxalines and isoxazoles. Cycloaddition reactions of nitrile oxides to alkynes yield isoxazoles directly, without a catalyst, but

N-Propargylamines: versatile building blocks in the construction of thiazole cores

• S. Arshadi,
• E. Vessally,
• L. Edjlali,
• R. Hosseinzadeh-Khanmiri and
• E. Ghorbani-Kalhor

Beilstein J. Org. Chem. 2017, 13, 625–638, doi:10.3762/bjoc.13.61

• syntheses of a series of multiply substituted thiazolidines 33 via the cyclization reaction of secondary N-propargylamines 32 with blocked N-isothiocyanate precursors 31. The desired N-isocyanates A are produced in situ upon heating or treatment with a base, in acetonitrile under microwave irradiation

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

• Jan Szabo,
• Julian Greiner and
• Gerhard Maas

Beilstein J. Org. Chem. 2017, 13, 579–588, doi:10.3762/bjoc.13.57

• been addressed only rarely, reactions with acid chlorides appear to be unknown. We have recently reported on the threefold carbamoylation of N,N’,N’’-tris(benzylamino)guanidinium salts with aryl isocyanates [3]. Concerning the reaction with carboxylic acids, it is known that TAG-Cl and formic acid on

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• ]. In this work, biaryl isocyanates 45 could be converted into phenanthridines 46, and aryl isocyanates 47 could be transformed into benzoxazoles 48 directly in refluxing toluene together with the simultaneous release of carbon dioxide. Presumably these reactions proceeded via iminophosphorane

• that afforded isocyanates 52. These were in turn treated in situ with catalyst 44 to afford the final products 50 via presumed iminophosphorane intermediates 53. Subsequently this research group used a very similar strategy for the synthesis of polysubstituted benzimidazoles 54 via sequential Ugi and

• catalytic aza-Wittig reactions (Scheme 16) [33]. It was reported that mixing 2-aminobenzoyl azides 55, carboxylic acids 56, isocyanides 57 with aldehydes 6 in methanol generated intermediates 58, which underwent rearrangement to isocyanates 59 in refluxing toluene. Finally, catalytic aza-Wittig reactions

Cross-linked cyclodextrin-based material for treatment of metals and organic substances present in industrial discharge waters

• Élise Euvrard,
• Nadia Morin-Crini,
• Coline Druart,
• Justine Bugnet,
• Bernard Martel,
• Cesare Cosentino,
• Virginie Moutarlier and
• Grégorio Crini

Beilstein J. Org. Chem. 2016, 12, 1826–1838, doi:10.3762/bjoc.12.172

• for the use of carboxylic acids and pyromellitic dianhydride, respectively, as agents to cross-linking CDs. Other cross-linking agents such as epichlorohydrin, ethylene glycol diglycidyl ether, glutaraldehyde, benzoquinone or isocyanates can be also used [1][12]. The main objective of the study was to

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• this case, the one-pot three-component reaction of isoquinoline and diphenyl phosphite with isocyanates 265 or isothiocyanates 266 furnished (dihydroisoquinolin-1-yl)phosphonates 267 or 268 in 96–99% yields under solvent-free conditions at room temperature (Scheme 55) [93]. A solvent-free

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

• -deficient isocyanates resulted in lower yields. We then turned our attention to the pivotal intramolecular allylic substitution reaction of 19 to access syn- and anti-pyrimidinones 23 and 24. As previously reported [31], this diastereodivergent coupling could indeed be realized as shown in Scheme 4. Based

Iodine-mediated synthesis of 3-acylbenzothiadiazine 1,1-dioxides

• Long-Yi Xi,
• Ruo-Yi Zhang,
• Lei Shi,
• Shan-Yong Chen and
• Xiao-Qi Yu

Beilstein J. Org. Chem. 2016, 12, 1072–1078, doi:10.3762/bjoc.12.101

• been developed to synthesize benzothiadiazine 1,1-dioxides and their analogues. The condensations of 2-aminobenzenesulfonamides with urea, isocyanates, carboxylic acid derivatives or other carbonyl reagents are the most used methods [12][13][14][15]. These reactions were usually carried out under harsh

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• to an additional stereodirecting group. Following this design and starting from the corresponding N-protected α-amino acid 46 different catalysts were easily synthesized by the reaction of the respective intermediate isocyanates 47 [93] with 9-epi-9-amino-9-deoxyquinine or 9-epi-9-amino-9

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• isocyanates and isothiocyanate gave ureido and thioureido persubstituted β-CD derivatives in a MW oven at 85 °C for 4 h (see Scheme 9). A multivalent azido-scaffold such as persubstituted 6-azido-6-deoxy-α-, β- or γ-CD with conformational constraints can be efficiently perfunctionalized in a MW- and ligand

Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time ¹³C CP-MAS solid-state NMR characterization

• Isabelle Mallard,
• Davy Baudelet,
• Franca Castiglione,
• Monica Ferro,
• Walter Panzeri,
• Enzio Ragg and
• Andrea Mele

Beilstein J. Org. Chem. 2015, 11, 2785–2794, doi:10.3762/bjoc.11.299

• epichlorohydrin [15][16], isocyanates [17][18], polycarboxylic acids [19][20] and anhydrides [21]. Following a slightly different approach, Trotta [18] and his group demonstrated that polymerization of cyclodextrins with a variety of synthetic equivalents of di- and tetracarboxylic acids provides an easy

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• synthesize and unstable [29]. Moreover, in our recent work we observed that reaction of pyrene with isothiocyanates proceeds more efficiently than an analogous reaction with isocyanates [7]. Additionally, compound 3a was transformed, using a standard procedure [30], to the corresponding phosphonic acid 4

CO₂ Chemistry

• Thomas E. Müller and
• Walter Leitner

Beilstein J. Org. Chem. 2015, 11, 675–677, doi:10.3762/bjoc.11.76

• molecule may be underestimated. Carbon dioxide is isoelectronic to highly reactive molecules such as isocyanates and ketenes (Figure 2). This implies that reactivity and kinetic limitations may be encountered much less frequently in the chemical conversion of carbon dioxide than generally assumed. To

The preparation of new functionalized [2.2]paracyclophane derivatives with N-containing functional groups

• Henning Hopf,
• Swaminathan Vijay Narayanan and
• Peter G. Jones

Beilstein J. Org. Chem. 2015, 11, 437–445, doi:10.3762/bjoc.11.50

• -38106 Braunschweig, Germany, Fax: (+49)531-391-5387 10.3762/bjoc.11.50 Abstract The two isomeric bis(isocyanates) 4,12- and 4,16-di-isocyanato[2.2]paracyclophane, 16 and 28, have been prepared from their corresponding diacids by simple routes. The two isomers are versatile intermediates for the

• analysis. Keywords: azides; crownophanes; cyclophanes; isocyanates; stereochemistry; X-ray analysis; Introduction Although hundreds of mono- und disubstituted derivatives of [2.2]paracyclophane [3][4] have been described since its initial preparation [5], relatively little is known about more highly

• structure determinations of organic isocyanates with the NCO group bonded to a phenyl ring. The dimensions of the isocyanate group observed for 28 [Cring–N 1.408(2), 1.419(2), N–C 1.194(3), 1.192(3), C–O 1.173(2), 1.174(2) Å; Cring–N–O 140.0(2), 136.9(2), N–C–O 172.6(2), 172.5(2)°] are closely similar to

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• triaminoguanidinium salts underwent a threefold carbamoylation with aryl isocyanates to furnish 1,2,3-tris(ureido)guanidinium salts, while p-toluenesulfonyl isocyanate led only to a mono-ureido guanidinium salt. With aryl isothiocyanates, 3-hydrazino-1H-1,2,4-triazole-5(4H)-thione derivatives were obtained. Compounds

• their reactions with isocyanates and isothiocyanates. Results and Discussion Synthesis of 1,2,3-tris(alkylamino)guanidinium salts 3 and 5 For the reasons explained in the Introduction, the synthesis of 1,2,3-tris(alkylamino)guanidinium salts from TAG-Cl (1) requires a two-step procedure. We have already

• with isocyanates When 1,2,3-tris(benzylamino)guanidinium salts 3 and 5-OTs were combined with three mol equivalents of aryl isocyanates 6a–c, triply carbamoylated salts 7a–f were obtained in good to high yields (Scheme 2). As was expected on the basis of the Hammett σp values [20], p-tolyl isocyanate