Allenol ether intermediates in the synthesis of 1,7-dioxaspiro [5.5]undec-4-enes and 1,6-dioxaspiro[4.5]dec-3-enes

Article abstract of DOI:10.1055/s-1991-26640

Sequential dialkylation of methoxyallene via the corresponding lithium derivatives gives 1,3-dialkylated methoxyallenes which undergo acid-catalysed ring closure to 1,7-dioxaspiro[5.5]undec-4-enes. Similarly, cyclic allenol ethers (2-vinylidenetetrahydropyrans) generated by rearrangement of 2-alkynyltetrahydropyrans cyclise on treatment with acid to give 1,6-dioxaspiro[4.5]dec-3-enes.