The products of the reaction of methyl propiolate with cyclohexene and some allyl and cyclohex-2-enyl silanes and stannanes (H-ene and M-ene adducts, and [2+ 2] and [3+ 2] cycloadducts) have been determined, and rationlised in terms of the probable reaction mechanism. The allylstannanes show only the M-ene reactions to give a mixture of the E- and Z-adducts, and it has been confirmed that the reaction of allylsilanes can give both the ...