Abstract
In the presence of BF 3 ·Et 2 O, condensation of CpW(CO) 2 (syn-π-2-methoxycarbonylpentadienyl) with aldehydes generated tungsten-η 4 -trans-diene cation in cold toluene, and hydrolysis of this salt afforded tungsten-π-allyl-anti-1,3-diols in good yields. This new synthesis of anti-1,3-diols represents an atypical Prins reaction that is applicable to normal aldehydes. The anti/syn ratios of 1,3-diols increased with an increase in the size of the aldehydes. These anti-1,3-diols were transformed into various complex oxygen heterocycles based on two demetalations: (1) conversion to an allyl cation followed by nucleophilic attack and (2) condensation with aldehydes via its CpW-(NO)Cl derivative, to give functionalized α-methylene butyrolactones. A semi-emperical calculation was performed to deduce the transition-state structure to rationalize the anti-stereoselectivity.