This compound, was a byproduct of the reaction of excess allyl magnesium chloride with the internal alkyn carbon of propargyl alcohol, yielding 2-methylene-4-penten-1-ol. This cyclic compound is postulated to arise from intra molecular cyclo addition of an intermediate vinyl carbanion to the terminal vinyl group of the intermediate, followed by hydrolysis.

1-Cycopent-1-yl carbinols are shown to be unexpected byproducts from the reaction of excess allyl Grignard with acetylenic alcohols. A mechanistic scheme is proposed.