Abstract
Abstract Thermal rearrangement of 4-aryloxymethyl-7-methylthiopyrano-[3,2-c]pyran-5-ones 6a-f afforded a number of hitherto unreported benzofuro[3,2-c]-6a,11a-dihydro-3,11adimethylthiopyranopyran-1-one 15a-e in good yields (60-67%) along with the exocyclic derivatives 16d,e,f as minor products (10-15%). Compounds 6a-f were in turn synthesized in 7285% yields by the thermal rearrangement of 4-(4'-aryloxybut-2'-ynylthio)-6-methylpyran-2-ones 5a-f. Compounds 5a-f were obtained in (50-55%) yields by the phase-transfer catalyzed alkylation of 4-mercapto-6-methyl-2-pyrone 3 with 1-aryloxy-4-chlorobut-2-yne 4a-f.
Highlights
4-Hydroxy-6-methyl-2-pyrone 1 is a natural product of polyketide origin.1 Many naturally occurring compounds2 contain the basic structural unit of 4-hydroxy(or methoxy)-6-alkyl-2-pyrone
Many more simple pyrones structurally related to elasnin have been synthesized and evaluated as inhibitors of several elastases
In a continuation of our work on the synthesis of bioactive heterocycles6 by the application of sigmatropic rearrangements7, we recently published8 the synthesis of fused thienopyrone heterocyclic systems
Summary
4-Hydroxy-6-methyl-2-pyrone (triacetic acid lactone) 1 is a natural product of polyketide origin.1 Many naturally occurring compounds2 contain the basic structural unit of 4-hydroxy(or methoxy)-6-alkyl-2-pyrone. Occurrence of [3,3] Sigmatropic rearrangement at the vinyl propargyl sulfide segment of compounds 5a-f may lead to polyheterocycles 6-8 while that at aryl propargyl ether part may generate polyheterocycles 9-11.
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