Reaction of N-Substituted 2-Oxochromen-3-carboxamides with Bromoderivatives of Zinc Enolates Prepared from Alkyl 2,2-Dialkyl-4,4-dibromo-3-oxoalkanoates and Zinc

摘要

Zinc enolates obtained from ethyl 2,2-dialkyl-4,4-dibromo-3-oxobutanoates and zinc react with N-substituted 2-oxochromen-3-carboxamides forming ethyl 3-{la-(R~3-carbamoyl)-2-oxo-la,7b-dihydrocyclo-propa[c]chromen-l-yl}-2,2-dialkyl-3-oxopropanoate isomer with a Z-position of methine hydrogens.Zinc enolates prepared from alkyl 2,2-dialkyl-4,4-dibromo-3-oxopentanoates and -hexanoates and zinc react with N-substituted 2-oxochromen-3-carboxamides to give rise to esters of 3-{l-alkyl-la-(R~3-carbamoyl)-2-oxo-la,7b-dihydrocyclopropa-[c]chromen-l-yl}-2,2-dialkyl-3-oxopropanoic acid as isomers with the E-position of the methine proton and the alkyl substituent.The reaction carried out in the presence of small quantities of THF and HMPA leads to the formation of 9c-alkyl-2-R~3-9b,9c-dihydro-5-oxa-2-azacyclopenta[2,3]-cyclopropa[l,2-a]naphthalene-l,3,4-triones.Zinc enolates from alkyl 2,2-dialkyl-4,4-dibromo-3-oxopentanoates and-hexanoates and zinc with the secondary amides of 2-oxochromen-3-carboxylic acid form alkyl 3-{2-oxo-la-(piperidinocarbonyl)-and 3-{6-R~1-la-(morpholinocarbonyl)-2-oxo-la,7b-dihydrocyclopropa[c]chromen-l-yl}-2,2-R~2,R~2-3-oxopropanoates as single geometrical isomers.