Synthesis, solid-state fluorescence properties, and computational analysis of novel 2-aminobenzo[4,5]thieno[3,2-d]pyrimidine 5,5-dioxides

• Kenichirou Yokota,
• Masayori Hagimori,
• Naoko Mizuyama,
• Yasuhisa Nishimura,
• Hiroshi Fujito,
• Yasuhiro Shigemitsu and
• Yoshinori Tominaga

Beilstein J. Org. Chem. 2012, 8, 266–274, doi:10.3762/bjoc.8.28

• -dioxides (3a–g), 2-amino-4-methylsulfanylbenzo[4,5]thieno[3,2-d]pyrimidine (6), and 2-amino-4-methylsulfanyl-7-methoxybenzo[4,5]furo[3,2-d]pyrimidine (7), were synthesized in good yields from heterocyclic ketene dithioacetals (1a–c) and guanidine carbonate (2a) or (S)-methylisothiourea sulfate (2b) in

• , we prepared new pyrimidine derivatives, which have solid-state blue fluorescence, by means of a one-pot synthesis, involving the reaction of ketene dithioacetals, amines, and guanidine carbonate in pyridine [5]. We have also reported the one-pot synthesis of a new, fluorescent, fused pyrimidine

• derivative 2,4-diaminoindeno[1,2-d]pyrimidin-5-one; this pyrimidine derivative, which was synthesized by heating a ketene dithioacetal, 2-[bis(methylsulfanyl)methylidene]indan-1,3-dione, under reflux with amine and amidine derivatives in pyridine solution, showed blue-green fluorescence in the solid state [6

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• elimination. This münchnone is in equilibrium with its ketene isomeric form 6, and a formal [2 + 2] cycloaddition with a second equivalent of imine generates the lactam (Scheme 3). The authors pointed out that the trapping of HCl by a sterically hindered base (NEtiPr2) is the key point in this methodology to

Approaches towards the synthesis of 5-aminopyrazoles

• Ranjana Aggarwal,
• Vinod Kumar,
• Rajiv Kumar and
• Shiv P. Singh

Beilstein J. Org. Chem. 2011, 7, 179–197, doi:10.3762/bjoc.7.25

• amino group (Scheme 24) [66]. Ketene dithioacetals 86 were utilized for the synthesis of corresponding pyrazole carbodithioates 88 by cyclization with methyl- or benzylhydrazine carbodithioate 87 in ethanolic TEA at room temperature. As before, the reaction proceeds via the nucleophilic substitution of

• corresponding 5-amino-3-arylamino-1-phenylpyrazole-4-carboxamides 90 (Scheme 25) [67]. Ketene S,S- and S,N-acetals or tetracyanoethylene 91 on reaction with 3-hydrazino-6-(p-tolyl)pyridazine afforded the 5-amino-4-cyanopyrazoles 92 (Scheme 26) [68]. Several thiazolylpyrazoles 97–100 bearing a variety of

• temperature, followed by treatment with methyl iodide afforded the novel ketene N,S-acetal 149. Reaction of 149 with hydrazine in refluxing ethanol gave the corresponding 5-aminopyrazole derivative 150. The reaction proceeds in the usual manner, i.e., loss of methylthio group by nucleophilic attack of

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• Paternò–Büchi reaction, spin-transition processes would be affected, and this may lead to interesting results. Abe et al. [14] investigated the effect of a sulfur atom on the stereoselective formation of oxetanes in Paternò–Büchi reaction of aromatic aldehydes with silyl O,S-ketene acetals to give trans-3

• -siloxyoxetanes and found that this was ca. 70/30 to 90/10. The trans-selectivity is explained by the sulfur atom effect in the silyl O,S-ketene acetal which controls the approach direction of the electrophilic oxygen of triplet n,π* aldehyde to the nucleophilic alkene. A fast ISC process of the triplet 1

Stereoselective synthesis of four possible isomers of streptopyrrolidine

• Debendra K. Mohapatra,
• Barla Thirupathi,
• Pragna P. Das and
• Jhillu S. Yadav

Beilstein J. Org. Chem. 2011, 7, 34–39, doi:10.3762/bjoc.7.6

• diastereomers 8a and 8b in a 3:2 ratio (as determined by NMR) (Scheme 2). Diastereomers 8a and 8b were easily separated by standard column chromatography on silica gel. The pioneering work on catalytic aldol reactions recently reported by Shibasaki [31] prompted us to investigate whether the ketene silyl acetal

• could be utilized for the aldol reaction in the presence of different Lewis acids to obtain a better selectivity particularly for (R)-tert-butyl (1-oxo-3-phenylpropan-2-yl)carbamate (6). To our surprise, when the reaction was carried out with the ketene silyl acetate at −78 °C, of the five Lewis acids

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• products [2]. Very recently we reported the use of 1,2-dihydro-1,1-dimethoxynaphthalen-2-ones 1 as protected precursors for the synthesis of both photocyclodimers and ketene-photocycloadducts of 1,2-naphtoquinones [3][4]. Here we report the preparation of – novel – 2a,8b-dihydrocyclobuta[a]naphthalene-3,4

Acid catalyzed cyclodimerization of 2,2-bis(trifluoromethyl)-4-alkoxy-oxetanes and -thietanes. Synthesis of 2,2,6,6-tetrakis(trifluoromethyl)-4,8-dialkoxy-1,5-dioxocanes and 3,3,7,7-tetrakis(trifluoromethyl)-9-oxa-2,6-dithia-bicyclo[3.3.1]nonane

• Viacheslav A. Petrov and
• Will Marshall

Beilstein J. Org. Chem. 2010, 6, No. 46, doi:10.3762/bjoc.6.46

• bis(trifluoromethyl)ketene and ethyl vinyl ether [9][10]. In the case of oxetane 1d, the main channel of the reaction involves stabilization of intermediates A and B by H+ elimination, leading to the formation of olefins 2d and 2e, respectively. Such a distinct difference in the reactivity of 1d may

Fused bicyclic piperidines and dihydropyridines by dearomatising cyclisation of the enolates of nicotinyl-substituted esters and ketones

• Heloise Brice,
• Jonathan Clayden and
• Stuart D. Hamilton

Beilstein J. Org. Chem. 2010, 6, No. 22, doi:10.3762/bjoc.6.22

• it into a silyl enol ether 9. Silyl enol ethers and ketene acetals are known to add effectively to pyridinium species in an intermolecular manner [42][43][44][45][46]. Thus 7 was converted to silyl enol ether 9 in excellent yield under standard conditions. A single geometrical isomer was obtained

• chloroformate to activate the pyridine without competing attack by the enolate. Next we extended the reaction to the cyclisation of a δ-nicotinyl butyrate ester 12 encouraged by the observations of Onaka [47], who demonstrated that silyl ketene acetals can be added (in an intermolecular fashion) to electron

• mixture of dienes 11 gave ester 12 after hydrogenation (Scheme 4). It proved challenging to isolate cleanly the silyl ketene acetal derived from 12, so instead we decided to form and cyclise the silyl derivative in a single pot. Thus, ester 12 was added to LDA at −78 °C, and the enolate quenched with

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• was developed for the reaction of imino esters with ketenes, leading to the stereoselective synthesis of ß-lactams [30]. Ketene was generated from the corresponding acid chloride with polymer-supported BEMP 17, and was reacted with an imino ester in a reaction catalyzed by the resin-supported quinine

• derivative 18. In this way, the handling and isolation of reactive ketene intermediates was directly avoided. A long and rigid linker to the resin was found to be ideal for obtaining good selectivities in this reaction. Nucleophilic scavenger 19 was used to remove excess reagents and byproducts. This three

Catalytic synthesis of (E)-α,β-unsaturated esters from aldehydes and 1,1-diethoxyethylene

• Rubén Manzano,
• Lidia Ozores,
• Andreas Job,
• Lars Rodefeld and
• Benjamin List

Beilstein J. Org. Chem. 2009, 5, No. 3, doi:10.3762/bjoc.5.3

• leads to the formation of water and CO2 as the only by-products (Scheme 1, eq 3) [23][24]. Here we describe as a new approach, the boronic acid-catalyzed condensation of ketene dialkyl acetal with aldehydes to furnish α,β-unsaturated esters in good yields and reliably high (E)-stereoselectivities

• (Scheme 1, eq 4). Although previously attempted under thermal conditions with poor success, our catalytic reaction is entirely new [25]. We reasoned that the reaction of readily available and inexpensive ketene diethyl acetal [26] or ketene dimethyl acetal (available from Aldrich) with aldehydes upon

• treatment with a suitable reagent or catalyst could readily lead to the corresponding unsaturated ester and ethanol or methanol as the only by-product. The use of ketene dialkyl acetals for organic transformations is infrequent [27]. To the best of our knowledge, they have been employed in [2+2

Aroylketene dithioacetal chemistry: facile synthesis of 4-aroyl- 3-methylsulfanyl- 2-tosylpyrroles from aroylketene dithioacetals and TosMIC

• H. Surya Prakash Rao and
• S. Sivakumar

Beilstein J. Org. Chem. 2007, 3, No. 31, doi:10.1186/1860-5397-3-31

• heterocyclic systems, examples of their participation in the cycloaddition reactions are rare. In continuation of our interest on ketene acetals [5][6][7] we considered that 1,3-dipolar cycloaddition of the anion generated from the von Leusen's reagent (p-tolylsulfonyl)methyl isocyanide (TosMIC) 2 to AKDTAs 1

Synthesis of highly substituted allenylsilanes by alkylidenation of silylketenes

• Stephen P. Marsden and
• Pascal C. Ducept

Beilstein J. Org. Chem. 2005, 1, No. 5, doi:10.1186/1860-5397-1-5

• yield, Scheme 2, Table 2. As expected, reactions with the more substituted ylide 4 were significantly slower than those with the parent ylide 5 (compare reaction temperatures and times, entries 1, 3 and 5 versus entries 2, 4 and 6). Increasing the steric bulk of the ketene substituent also slows the

• reaction, in line with our expectations, exemplified by the reactions of cyclohexyl-substituted ketene 1d (entries 7 and 8, compared with entries 1–6). In almost all cases, if reactions were left for extended periods beyond consumption of starting material, small quantities of desilylated allenes were

• silylketenes with reactive ylides involves deprotonation by the basic reagent to generate ynolate anions. Clearly, since such a pathway cannot operate with the substituted ketenes used here other mechanisms are at play, which may include nucleophilic desilylation or ketene oligomerisation initiated by