O-Methylarenehydroxamates as ortho-lithiation directing groups. Titanium(III)-mediated conversion of O-methyl hydroxamates to primary amides
摘要:
Reaction of O-methyl benzohydroxamates 2a-c with sec-butyllithium in the presence of TMEDA at -40-degrees-C regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g. 3). These dilithio species react avidly with a wide spectrum of electrophilic reagents, including alkyl halides, giving adducts which on reduction with TiCl3 are converted into ortho-substituted primary benzamides in excellent yields. Ortho lithiation of O-methyl benzohydroxamates is thus formally equivalent to ortho lithiation of primary benzamides themselves. The utility of these synthetic operations is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups. The conversion of 0-methyl hydroxamates to primary amides is shown to be general, as exemplified by transformation of 14a-f to 15a-f.O-Methyl 2-methylbenzohydroxamate (4a) undergoes regiospecific dilithiation on nitrogen and on the methyl group when treated with sec-butyllithium at -70-degrees-C. These dilithio species react with DMF or ''Weinreb-type'' amides to give condensation products which cyclize to N-methoxyisoquinolin-1(2H)-ones under mildly acidic conditions. Removal of the N-methoxy moiety under conditions analogous to those used for O-methyl benzohydroxamate provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency. This process is exemplified by the synthesis of isoquinolin-1(2H)-one 9a, its 3-n-butyl congener 9b, and the tricyclic isoquinolin-1 (2H)-ones 20a and 20b from O-methyl 2-methylbenzohydroxamate (4a).
O-Methylarenehydroxamates as ortho-lithiation directing groups. Titanium(III)-mediated conversion of O-methyl hydroxamates to primary amides
摘要:
Reaction of O-methyl benzohydroxamates 2a-c with sec-butyllithium in the presence of TMEDA at -40-degrees-C regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g. 3). These dilithio species react avidly with a wide spectrum of electrophilic reagents, including alkyl halides, giving adducts which on reduction with TiCl3 are converted into ortho-substituted primary benzamides in excellent yields. Ortho lithiation of O-methyl benzohydroxamates is thus formally equivalent to ortho lithiation of primary benzamides themselves. The utility of these synthetic operations is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups. The conversion of 0-methyl hydroxamates to primary amides is shown to be general, as exemplified by transformation of 14a-f to 15a-f.O-Methyl 2-methylbenzohydroxamate (4a) undergoes regiospecific dilithiation on nitrogen and on the methyl group when treated with sec-butyllithium at -70-degrees-C. These dilithio species react with DMF or ''Weinreb-type'' amides to give condensation products which cyclize to N-methoxyisoquinolin-1(2H)-ones under mildly acidic conditions. Removal of the N-methoxy moiety under conditions analogous to those used for O-methyl benzohydroxamate provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency. This process is exemplified by the synthesis of isoquinolin-1(2H)-one 9a, its 3-n-butyl congener 9b, and the tricyclic isoquinolin-1 (2H)-ones 20a and 20b from O-methyl 2-methylbenzohydroxamate (4a).
Tandem C–C coupling – intramolecular acetylenic Schmidt reaction under Pd/C–Cu catalysis
作者:Venkateswara Rao Batchu、Deepak Kumar Barange、Dinesh Kumar、Bukkapattanam R. Sreekanth、K. Vyas、E. Amarender Reddy、Manojit Pal
DOI:10.1039/b617823e
日期:——
A new one-pot reaction for the regioselective construction of a six-membered fused N-heterocyclic ring leading to isoquinolones under Pd/CâCu catalysis is described.
描述了一种新的单锅反应,通过Pd/C–Cu催化,实现对六元并联N-杂环的选择性构建,生成异喹啉酮。
O-Methylarenehydroxamates as ortho-lithiation directing groups. Titanium(III)-mediated conversion of O-methyl hydroxamates to primary amides
作者:Lawrence E. Fisher、Joan M. Caroon、Jahangir、S. Russell Stabler、Scott Lundberg、Joseph M. Muchowski
DOI:10.1021/jo00066a014
日期:1993.7
Reaction of O-methyl benzohydroxamates 2a-c with sec-butyllithium in the presence of TMEDA at -40-degrees-C regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g. 3). These dilithio species react avidly with a wide spectrum of electrophilic reagents, including alkyl halides, giving adducts which on reduction with TiCl3 are converted into ortho-substituted primary benzamides in excellent yields. Ortho lithiation of O-methyl benzohydroxamates is thus formally equivalent to ortho lithiation of primary benzamides themselves. The utility of these synthetic operations is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups. The conversion of 0-methyl hydroxamates to primary amides is shown to be general, as exemplified by transformation of 14a-f to 15a-f.O-Methyl 2-methylbenzohydroxamate (4a) undergoes regiospecific dilithiation on nitrogen and on the methyl group when treated with sec-butyllithium at -70-degrees-C. These dilithio species react with DMF or ''Weinreb-type'' amides to give condensation products which cyclize to N-methoxyisoquinolin-1(2H)-ones under mildly acidic conditions. Removal of the N-methoxy moiety under conditions analogous to those used for O-methyl benzohydroxamate provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency. This process is exemplified by the synthesis of isoquinolin-1(2H)-one 9a, its 3-n-butyl congener 9b, and the tricyclic isoquinolin-1 (2H)-ones 20a and 20b from O-methyl 2-methylbenzohydroxamate (4a).