Synthesis of Sterically Congested Acetic Acid Derivatives: The Reaction of Hindered α-Oxo Esters with Pentasubstituted Aryl Grignard Reagents
作者:A. F. Hegarty、P. O'Neill
DOI:10.1055/s-1993-25911
日期:——
The reactions of pentamethylphenylmagnesium bromide and pentachlorophenylmagnesium chloride with tert-butyl 2-oxo-3,3-dimethylbutanoate to give the 2-aryl-2-hydroxy-3, 3-dimethylbutanoate esters were investigated. Attempted acid catalysed dealkylation of the tert-butyl 2-hydroxy-3,3-dimethyl-2-(pentamethylphenyl) butanoate to the corresponding acid was accompanied by skeletal rearrangement, while the corresponding pentachlorophenyl ester reacted normally. The corresponding α- pentachlorophenyl α-α-tert-butyl acetic acid 15 was synthesised without rearrangement. The reaction of pentachlorophenylmagnesium chloride with diisopropyl oxalate gave the α-oxo ester 18, which reacted with pentamethylphenylmagnesium bromide to afford the unsymmetrical diarylacetate ester 22. The corresponding acid chloride 25 could not be converted to the interesting unsymmetrical diarylketene 26.
研究了五甲基苯基溴化镁和五氯苯基氯化镁与2-氧代-3,3-二甲基丁酸叔丁酯的反应生成2-芳基-2-羟基-3,3-二甲基丁酸酯。尝试将2-羟基-3,3-二甲基-2-(五甲基苯基)丁酸叔丁酯酸催化脱烷基化为相应的酸,同时伴随骨架重排,而相应的五氯苯酯反应正常。无需重排即可合成相应的α-五氯苯基α-α-叔丁基乙酸15。五氯苯基氯化镁与草酸二异丙酯反应得到α-氧代酯18,其与五甲基苯基溴化镁反应得到不对称二芳基乙酸酯22。相应的酰氯25不能转化为有趣的不对称二芳基乙烯酮26。