Preparation of Titanated Alkoxyallenes from 3-Alkoxy-2-propyn-1-yl Carbonates and (η2-Propene)Ti(O-i-Pr)2 as an Efficient Ester Homoaldol Equivalent

3-Alkoxy-2-propyn-1-yl carbonates (2) react with a divalent titanium reagent (eta(2)-propene)Ti(O-i-Pr)(2) to afford titanated alkoxyallenes 1 which, in turn, react with aldehydes regiospecifically to provide the corresponding gamma-addition products in good to excellent yields, thus affording a convenient method for synthesizing gamma-hydroxy esters 3 and/or gamma-butyrolactones 4.