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The esterifications of 9-(hydroxyimino)-4-methyl-8,9-dihydrofuro[2,3-h]chromen-2-one (4)with acid chlorides afforded normal oxime-esters 3a-e in 35-78% yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger,whereas the reactions gave unexpected 8-substituted products N-(8-chloro-4-methyl-2-oxo-2H-furo-[2,3-h]chromen-9-yl)amides (5a-c) and 4-methyl-2,9-dioxo-8,9-dihydro-2H-furo[2,3-h]chromen-8-ylcarboxyloates (6d-e)by using excessive acid chlorides.The structures of 10 new compounds were determined by ~1H NMR,~(13)C NMR,MS and HRMS,and the possible mechanism for the formation of unexpected products 5a-c and 6d-e was also proposed.
The esterifications of 9- (hydroxyimino) -4-methyl-8,9-dihydrofuro [2,3-h] chromen-2-one (4) with acid chlorides afforded normal oxime-esters 3a-e in 35-78% yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger, while the reactions gave unexpected 8-substituted products N- (8-chloro-4-methyl-2-oxo-2H-furo- [2,3-h] chromen-9 8-ylcarboxyloates (6d-e) by using excessive acid (5a-c) and 4-methyl-2,9- dioxo-8,9-dihydro- chlorides. The structures of 10 new compounds were determined by ~ 1H NMR, ~ (13) C NMR, MS and HRMS, and the possible mechanism for the formation of unexpected products 5a-c and 6d-e was also proposed.