Further Studies on Quinone Diels-Alder Reactions with 1,3,3-Trimethyl-2-vinylcyclohexenes: Regioselective Synthesis of 12-Methyl-podocarpane Diterpenes and Isolation of a Hetero Diels-Alder Product from 1,4-Benzoquinone
摘要:
Diels-Alder reactions of 2-[(E)-beta-alkoxyvinyl]-1,3,3-trimethylcyclohexenes with 2-methoxy-3-methyl-1,4-benzoquinone regioselectively produce adducts possessing the 12-methyl-podocarpane ring skeleton. In addition, in the reaction with 1,4-benzoquinone an unusual hetero Diels-Alder product involving the C=O group of the quinone is found in low yield.