| Abstract
| - Iron(III) halides have proven to be excellent catalysts in the coupling of acetylenes and aldehydes.When terminal acetylenes were used the main products obtained were 1,5-dihalo-1,4-dienes with(E,Z)-stereochemistry contaminated in some cases with (E)-α,β-unsaturated ketones. The formercarbonyl derivatives were the sole products isolated when nonterminal aromatic alkynes were used.When homopropargylic alcohols were used, a Prins-type cyclization occurred yielding 2-alkyl-4-halo-5,6-dihydro-2H-pyrans. In addition, anhydrous ferric halides are also shown to be excellentcatalysts for the standard Prins cyclization with homoallylic alcohols. Isolation of an intermediateacetal, calculations, and alkyne hydration studies provide substantiation of a proposed mechanism.
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