Some reactions of acetylenic alcohols (1983)
AuthorsVannoort, R. W.show all
The lithium aluminium hydride (deuteride) reduction of 2,2-di-(methoxymethyl)-3-phenylhex-4-yn-3-ol (98), in a range of ether solvents has been examined. Intramolecular solvation of the aluminium atom during the reduction process has been identified and the mode of formation of the reaction products discussed. Isolation and identification of the unexpected cyclopropane derivatives (115) and (116) resulted in extending studies to encompass the reaction of 1-methoxy- 2,2-dimethyl-3-phenylhex-4-yn-3-ol (90b) with lithium aluminium hydride (deuteride). Cyclopropane derivatives were also isolated and the mode of formation of propenyl-cyclopropane (125) established. In an attempt to determine the effect of ring size in intramolecular solvation, 1-methoxy-2-phenylpent-3-yn-2-ol (136), 1-methoxy-3-phenylhex-4-yn-3-ol (137) and 7-methoxy-4-phenylhept- 2-yn-4-ol (138), were synthesized and their reactions with lithium aluminium hydride (deuteride) in diethyl ether, tetrahydrofuran or 2,5-dimethyltetrahydrofuran were studied. It was observed that intramolecular solvation occurs for methoxy compounds (136) and (137) but not for (138); these results are discussed. A semi-quantitative rate comparison was made for the reactions of 2,2-dimethyl-3-phenylhex-4-yn-3-ol (90a), its 1-methoxy-(90b) and 1,1-dimethoxy-(98) derivatives, when reduced by lithium aluminium hydride (deuteride) in benzene solvent. Similar work was undertaken on 2-phenylpent-3-yn-2-ol (18), its 1-methoxy derivative (136), and methoxy alkynols (137) and (138). Rate enhancement was only observed when the alkynols contained an internal ether moiety.