Synthesis of Nonracemic 9-(1-Methoxycarbonylethyl)-1,2,3,4-tetrahydrocarbazole

A new approach has been proposed to the synthesis of indole derivatives containing a chiral substituent at the nitrogen atom, comprizing Fischer indolization of phenylhydrazines with a chiral substituent at the -nitrogen atom. The initial hydrazines were obtained by the alkylation (Mitsunobu reaction applying optically active esters of lactic acid) of anilines containing an electron-accepting substituent at the amino group. Subsequent removal of the activating acceptor grouping was realized by nitrosation of the chiral secondary aniline followed by reduction of the corresponding N-nitroso compound.     

Asymmetric enolate alkylation via templation with chiral synthetic receptors

C₃-Symmetric chiral receptors have been developed for enantioselective alkylation of sodium enolates of active methylene compounds. It has been demonstrated that a 1:1 binding complex forms between these receptors and sodium enolates in THF-d₈/CD₃CN by ¹H NMR titration experiments. Moderate enantiomeric enrichment of the benzylation product of 2-acetylcyclohexanone has been demonstrated using this strategy. Templation of enolate alkylation by synthetic receptors represents a new approach to asymmetric induction.     

Mechanism and scope of salen bifunctional catalysts in asymmetric aldehyde and α-ketoester alkylation

Metal complexes of C₂-symmetric Lewis acid/Lewis base salen ligands provide bifunctional activation resulting in rapid rates in the enantioselective addition of diethylzinc to aldehydes (up to 92% ee). Further experiments probed the reactivity of the individual Lewis acid and Lewis base components of the catalyst and established that both moieties are essential for asymmetric catalysis. These catalysts are also effective in the asymmetric addition of diethylzinc to α-ketoesters. This finding is significant because α-ketoesters alone serve as their own ligands to accelerate racemic 1,2-carbonyl addition of Et₂Zn and racemic carbonyl reduction. The latter proceeds via a metalloene pathway, and often accounts for the predominant product. Singular Lewis acid catalysts do not accelerate enantioselective 1,2-addition over these two competing paths. The bifunctional amino salen catalysts, however, rapidly provide enantioenriched 1,2-addition products in excellent yield, complete chemoselectivity, and good enantioselectivity (up to 88% ee). A library of the bifunctional amino salens was synthesized and evaluated in this reaction. The utility of the α-ketoester method has been demonstrated in the synthesis of an opiate antagonist.     

用甲基叔丁基甲醚对苯酚叔丁基化的反应研究

目前我国生产对叔丁基苯酚的方法通常以酚类为原料，烯烃或醚类为烷基化试 剂，其中异丁烯是主要烷基化试剂，但异丁烯在储存、运输等方面存在着一定的弊 端．采用直接以甲基叔丁基甲醚为烷基化试剂，研究了苯酚与甲基叔丁基甲醚的烷 基化反应．并对各影响因素进行了讨论，其中催化剂用量和原料比对反应影响最大 ，温度次之，反应时间影响最小．实验中得出了制备反应的最佳条件；苯酚转化率 大于85％，对叔丁基苯酚产率为78％，得到较理想产率．并与以异丁烯为烷基化试 剂进行了比较，具有成本低、流程短、操作简便、安全等特点，应用前景非常好．     

Alkylation of salts ofN-nitrohydroxylamines with chloromethylnitramines

The reactions of Ag-salts ofN-nitmhydroxyumines withN-methyl-N-chloromethylnitramine afford mainly products ofO-alkylation, whereas the reactions of the corresponding Li-, Na-, K-, Mg-, and NH₄-sals in the presence of tetrabutylammonium (TBAB) give mainly products ofN-alkylation. The reactions of the corresponding. NH₄-salts with bis-(chloromethyl)nitramine in the presence of TBAB lead solely to products ofO-alkylation. Increasing in the amount of TBAB results in the appearance of theN-isomer.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1740–1744, July, 1996.     

Alkylation of cyclododecanone with α,ω-dibromoalkanes under conditions of phase-transfer catalysis

Alkylation of cyclododecanone with ,-dibromoalkanes Br(CH) _n Br (n=3, 4, 5) under conditions of phase-transfer catalysis in the presence of KOH results in the formation of either bicyclic ketones forn=3 and 5 or a mixture of bicyclic and spirocyclic ketones forn=4.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1436–1438, August, 1994.     

Catalytic, asymmetric synthesis of α,α-disubstituted amino acids

Copper(salen) complex 1 has been found to catalyse the asymmetric alkylation of enolates derived from a variety of amino acids. There is a clear relationship between the size of the side chain in the substrate and the enantioselectivity of the process, so that the enantioselectivity decreases in the order alanine>aminobutyric acid>allylglycine>leucine>phenylalanine>valine. A transition state model which accounts for the influence of the size of the side chain on the enantioselectivity of the reactions is presented.     

A new method for the synthesis ofN-methylmorpholinium 4-aryl-5-cyano-2-oxo-1,2,3,4-tetrahydropyridine-6-thiolates and their properties

N-Methylmorpholinium 4-aryl-5-cyano-2-oxo-2-oxo-1,2,3,4-tetrahydropyridine-6-thiolates were obtained by the condensation of aromatic aldehydes, cyanothioacetamide, and Meldrum's acid in the presence ofN-methylmorpholine. They were then used in the syntheses of substituted 6-alkylthio-3,4-dihydropyridin-2(1H)-ones and 4,5-dihydrothieno[2,3-b]pyridin-6(7H)-ones. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1852–1856, October, 1997.     

Combined application of 2D NMR correlation methods and ab initio chemical shift calculations to the structure determination of new heterocyclic compounds

The combined use of 2D NMR correlation methods and ab initio chemical shift calculations is efficient and, in some cases, virtually the only way to determine the structures of new organic compounds. This approach enabled us to establish the structure of the major unusual product of the three-component reaction of imidazo[1,5-a]quinoxalin-4-one, bis(2-chloroethyl)amine hydrochloride, and potassium carbonate in DMF. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2172–2179, December, 2006. Dedicated to Professor A. V. Il’yasov on the occasion of his 70th birthday.     

HY沸石上2,6-二叔丁基萘的择形合成

 研究了脱铝HY沸石（n（Si）／n（Al）＝3．8）上萘（naph）的\r\n选择性叔丁基化反应．结果表明，八面沸石对该反应过程有较好的择形\r\n催化作用，两种异构化产物（2，6－二叔丁基萘和2，7－二叔丁基萘）\r\n之间存在着热力学平衡，即两种异构化产物可在酸性中心位上相互转化\r\n．在以叔丁醇为烷基化试剂，WHSV＝2h－1，n（t－BuOH）／n（naph）\r\n＝3，反应温度为120℃的反应条件下，萘的转化率可达98．43％，β－\r\n位选择性可高达100％，二叔丁基萘收率可达74．34％，2，6－二叔丁\r\n基萘／2，7－二叔丁基萘质量比为6．24．