Efficient synthesis of 5-substituted 2-aryl-6-cyanoindolizines via nucleophilic substitution reactions

2-Aryl-6-cyano-7-methyl-5-indolizinones were successfully converted into 2-aryl-5-chloro-6-cyano-7-methylindolizines. The obtained 5-chloroindolizines readily underwent nucleophilic substitution at position 5 leading in high yields to novel 5-functionalised indolizines.     

Syntheses of various 5-(bromoaryl)-substituted uracils

The Suzuki Pd(0)-catalyzed coupling between arylboronic acids and aryl bromides or iodides in weakly alkaline medium, previously further developed by us, has been used for regioselective preparation of 5-(2′-bromo-5′-furyl)-, 5-(2′-bromo-4′-furyl)-, 5-(2′-bromo-5′-thienyl)-, 5-(2′-bromo-4′-thienyl)-, 5-(4′-bromo-2′-thiazolyl)-, 5-(3′-bromophenyl)-, 5-(6′-bromo-2′-pyridyl)- and 5-(4′-bromo-2′-pyrimidyl)-substituted 2,4-di-t-butoxypyrimidines. In the coupling between 2,4-di-t-butoxy-5-pyrimidineboronic acid and the nine different aryl dibromides that were tried as coupling partners, only the 2,4- and 2,5-dibromothiazoles did not give satisfactory yields, 15% and 0%, respectively. The other seven aryl dibromides gave the desired 5-(bromoaryl)-2,4-di-t-butoxypyrimidines in 58-89% yield. Attempts to synthesise 2,4-di-t-butoxy-5-(2′-bromo-4′-thienyl)pyrimidine from 2-bromo-4-iodothiophene failed. Dealkylation of the 5-(bromoaryl)-2,4-di-t-butoxypyrimidines in 2.5 M hydrochloric acid gave the corresponding 5-(bromoaryl)uracils in almost quantitative yields.     

Cyclisation reactions of 2-substituted benzoylphosphonates with trialkyl phosphites via nucleophilic attack on a carbonyl-containing ortho substituent

Dimethyl 2-acetoxy- and dimethyl 2-benzoyloxy-benzoylphosphonate undergo cyclisation and deoxygenation in the presence of excess trimethyl phosphite to give dimethyl (3-methyl-1-benzofuran-2-yl)phosphonate and dimethyl (3-phenyl-1-benzofuran-2-yl)phosphonate, respectively. The reaction pathway has been shown to involve phosphite attack on initially formed tricyclic dioxaphospholane intermediates with the subsequent loss of two molecules of trimethyl phosphate. In the absence of additional trimethyl phosphite the initially formed tricyclic dioxaphospholane intermediates lose one molecule of trimethyl phosphate and then undergo a novel rearrangement to give β-ketophosphonates. The mechanism for this reaction helps explain some previously reported epoxide rearrangements. In contrast, the initially formed anionic intermediate from the reaction of dimethyl 2-benzoyloxymethylbenzoylphosphonate with trimethyl phosphite undergoes decomposition to give a carbene intermediate which is trapped by the trimethyl phosphite to give an ylidic phosphonate.     

Palladium-catalyzed synthesis of terminal acetals via highly selective anti-Markovnikov nucleophilic attack of pinacol on vinylarenes, allyl ethers, and 1,5-dienes

A palladium-catalyzed reaction of vinylarenes, allyl ethers, and 1,5-dienes with pinacol proceeded via a selective anti-Markovnikov nucleophilic attack to afford corresponding terminal acetals as major products. The bulkiness of pinacol was found to be critical in controlling the regioselectivity.     

New versatile Pd-catalyzed alkylation of indoles via nucleophilic allylic substitution: controlling the regioselectivity

[reaction: see text] A systematic study addressed toward the optimization of the Pd-catalyzed alkylation of indoles by allylic carbonates is presented. The protocol uses a catalytic amount of [PdCl(pi-allyl)](2)/phosphine as a promoting agent, providing allylindoles in excellent yields. The regioselectivity of the reaction can be controlled by a proper choice of the base and the reaction media. The method proved to be effective also for intramolecular allylic alkylations of indolyl carbonates, providing a flexible route to fused indole alkaloids.     

Syntheses of 4-, 5-, 6-, and 7-substituted tryptamine derivatives and the use of a bromine atom as a protecting group

Orthogonal syntheses of 4-, 5-, 6-, and 7-chloro substituted tryptamine derivatives were performed under the Grandberg–Zuyanova-modified Fisher indole-synthesis conditions. In the 4- and 6-substituted tryptamine cases, a bromine atom was utilized as an easily cleavable protecting group, which allowed complete regiocontrol. In addition, a chlorine substituent was preserved in the debromination step and could be utilized as a synthetic handle for late-stage diversification under modern Pd(0) catalysis conditions.     

Syntheses of 4- and 6-substituted thiazolo[4,5-c]pyridines

A general synthetic approach to 4,6-substituted thiazole[4,5-c]pyridines, involving a novel one-pot thiol deprotection-cyclization key step, is described.     

Electrophilic substitution of 5- and 6-substituted benzo-1,4-dioxanes

The compositions of the products of bromination, nitration, and acetylation of 5- and 6-fluoro(chloro, nitro, methoxy, methyl, formyl, and carboxy)benzo-1,4-dioxanes were established. The reactivity indexes and the characteristics of the UV spectra of the starting compounds were calculated by the self-consistent-field (SCF) MO LCAO method within the Pariser-Parr-Pople (PPP) and CNDO/2 CI (complete neglect of differential overlap with configuration interaction) approximations, and the results were compared with the experimental data.Translated from Khimiya Geterotsiklicheskikh Soedinenii,No. 11, pp. 1465–1471, November, 1978.     

Syntheses of various 5-(3′-substituted phenyl)uracils

The Suzuki Pd(0)-catalysed coupling between arylboronic acids and aryl bromides or iodides in weakly alkaline medium has been used for the preparation of 5-(3′-chlorophenyl)-, 5-(3′-iodophenyl)-, 5-(3′-aminophenyl)-, 5-(3′-azidophenyl)-, 5-(3′-methylthiophenyl)- and 5-(3′-styryl)-substituted 2,4-di-t-butoxypyrimidines. In the coupling between 2,4 di-t-butoxy-5-pyrimidineboronic acid and the six different aryl halides that were used as coupling partners, only 1-azido-3-bromobenzene did not give satisfactory yields, 18%. The other five aryl halides gave the desired 5-(3′-substituted phenyl)-2,4-di-r-butoxypyrimidines in 41–92% yield. Dealkylation of these five 5-(3′-substituted phenyl)-2,4-di-t-butoxypyrimidines in 2.5M hydrochloric acid gave the corresponding 5-(bromoaryl)uracils in almost quantitative yields. 5-(3′-Azidophenyl)uracil was prepared in 43% yield directly from 5-(3′-aminophenyl)-2,4-di-r-butoxypyrimidine.     

Syntheses of regioisomerically pure 5- or 6-halogenated fluoresceins

Three routes to regioisomerically pure 5- and 6-iodofluoresceins or 5- and 6-bromofluoresceins are described. The first, shown in Scheme 1, involves diazotization/iodination of the corresponding aminofluoresceins. In the second approach (Scheme 2) a mixture of regioisomeric fluoresceins was prepared, and the 5-bromo isomers were isolated as the ring closed diacetates 9b and 11 by fractional crystallization. Scheme 3 shows an approach to sulfonic acid derivatives 3 and 4 of 5-iodofluorescein. This is the most convenient procedure of the three, and it is particularly useful as sulfofluoresceins have more favorable water solubility characteristics than fluoresceins that lack the sulfonic acid group.     

Kinetics of nucleophilic attack on coordinated organic moieties: XXVI. An extended nucleophilicity scale for nucleophilic addition to the cation [Fe(CO)3(1-5-η-C6H7)]+

A nucleophilicity scale is established for the addition of ca. 40 different nucleophiles to the cyclohexadienyl ring of the cation [Fe(CO)₃(1-5-η-C₆H₇)]⁺ (I). The factors controlling nudeophilicity towards cation I are discussed, and comparisons made with data for reactions of the nucleophiles with other model organic and inorganic substrates such as MeI and trans-[PtCl₂py₂].     

Electronic control of the stereochemistry of electrophilic and nucleophilic attack on double bonds in 6-membered rings

CNDO and ab initio MO calculations reveal a deformation of the π^* and π orbitals of cyclohexene in the axial directions, thus providing a reasonable explanation for the axial attack on cyclohexene either by electrophiles or by nucleophiles. It is shown in the case of 1-butene by an ab initio calculation that this orbital deformation is a result of the mixing of the π and σ orbitals of the double bond under the influence of the allylic C-C bond.     

5-取代苯氨基-6-苯基-1,2,4-三嗪-3-酮的合成

苯甲铣基-N-取代茜基硫代甲酰胺与氨基脲缩合后,环化可何成4,6-二取代-5-硫酮-1,2,4-三嗪-3-酮.本文报道将其缩氨基脲中硫甲基化,然后在碱性条件下, 改变成环方式,合成九个5-取代苯氨基-6-苯基-1,1,4-三嗪1-3-酮.它们的结构经元素分析,红外,核磁,质谱等予以证实.探讨了两种不同成环原因.     

Synthesis of 1-oxa-2-silacyclopentane derivatives via intramolecular nucleophilic attack at silicon

Metalation of (HSiMe₂)₃CH with lithium diisopropylamide (LDA) in THF gives (HSiMe₂)₃CLi, which reacts with ethylene oxide, propylene oxide, 1,2-epoxy butane, 1,2-epoxy pentane, 1,2-epoxy hexane, and epichlorohydrin to give the corresponding 1-oxa-2-silacyclopentane derivatives. Then, glycidylmethacrylate (GM) random copolymers with styrene (St) (in a 1:1 and 1:3 mol ratio) were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. Both types of copolymers were treated with (HSiMe₂)₃CLi to give new modified copolymers. The reaction of (HSiMe₂)₃CLi with epoxides on the side chains of the copolymers does not lead to intramolecular nucleophilic attack contrary to simple epoxides. All the products have been characterized by spectroscopic techniques.     

Syntheses of 6-Guanidino-hexoses and 5-Guanidino-pentoses

Abstract

Guanidinations of primary amines were performed with 3,5-dimethylpyrazolylformamidinium nitrate. 6-Deoxy-6-guanidino derivatives of unprotected N-acetyl-glucosamine and of glucosamine were prepared, with both products existing as pyranoses. In the pentose series, 5-deoxy-5-guanidinio-D-xylose nitrate (17) and -D-arabinose nitrate (22) were synthesized. For both compounds, besides some α-D-xylo-pyranose and β-D-arabino-pyranose, mainly the furanoses are found.     

Intramolecular nucleophilic attack at silicon in o-silylbenzyl alcohols. Generation of allyl and benzyl anion equivalents

Substituted silyl ethers of o-bromobenzyl alcohols and the derived o-silylbenzyl alcohols were used to transfer allyl and benzyl groups from silicon to the electrophiles benzaldehyde and benzophenone in excellent yields. γ-Oxidosilane intermediates (and possibly hypercoordinated silicon intermediates) are postulated.     

胺、醇、醚类化合物电离能的自相关拓扑研究

原子的染色序数 fi 定义为 :fi=gi·xi,式中 gi 为原子i在分子中的序数 ,xi 为其染色系数 .基于fi 建立改进的原子序数自相关拓扑指数mF ,其中的1F对烷烃及其衍生物具有良好的结构选择性 .使用第一电离能 (Ip)与0 F ,1F的数量关系模型对 32种脂肪族胺、醇、醚进行估算、预测 ,结果令人满意