The efficient succinylation of the sterically hindered tertiary alcohols 1 was performed by reaction with succinic acid monomethyl and monoallyl ester (4a and 4b), respectively, in CH2Cl2 in the presence of dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine under high pressure to give the methyl and allyl succinates 5a and 5b, respectively, in high yields. The succinates 5a,b were efficiently converted into the hemisuccinate 3a by treatment with lithium propyl mercaptide or by palladium(0)-catalyzed deallylation.
Succinates of the tertiary hydroxy group having a formyl group in the structure were conveniently synthesized by oxidative cleavage of dihydropyrans prepared from lactones via coupling of ketene acetal triflates and zinc homoenolates.
Efficient method for preparation of N-methoxy-N-methyl amides by reaction of lactones or esters with Me2AlClMeONHMe·HCl
作者:Takeshi Shimizu、Katsuhisa Osako、Ta-i Nakata
DOI:10.1016/s0040-4039(97)00429-2
日期:1997.4
The reaction of a lactone or an ester with dimethylaluminum chloride and N, O-dimethylhydroxylamine hydrochloride provided an efficient method for preparation of N-methoxy-N-methyl amide.