Heteropoly acid catalyzed synthesis of 8-methyl-2-aryl/alkyl-3-oxabicyclo[3.3.1]non-7-ene derivatives through (3,5)-oxonium-ene reaction

A variety of aldehydes undergo a smooth coupling with (4-methylcyclohex-3-en-1-yl)methanol in the presence of 2 mol % of phosphomolybdic acid in dichloromethane to afford 3-oxabicyclo[3.3.1]non-7-ene in good yields through 3,5-oxonium-ene cyclization under mild conditions. The use of inexpensive, nontoxic, and readily available heteropoly acid catalyst makes this method simple, convenient, and environmental-friendly.     

Phenylselenoetherification of Some Δ5-Alkenols in the Presence of Pyridine, Ag2O, and AgOAc as Additives

Summary. An improved procedure for intramolecular cyclization of some ⁵-alkenols using PhSeX (X=Cl, Br) was developed. We found that cyclization can be facilitated in the presence of pyridine, Ag₂O, and AgOAc as additives. Thus, a catalytic amount of additive influenced higher yields and equimolar amounts achieved almost quantitative yields under extremely mild experimental conditions. The effect of the halide ion of the selenylating reagent was not significant.Received October 21, 2002; accepted (revised) November 13, 2002 Published online August 28, 2003     

Reaction of Some Alkenols with Tetrachloromethane

Summary.  The reaction of some alkenols with tetrachloromethane in the presence of a radical initiator was investigated. Regarding the effects of structural features of the starting alkenol (number and position of methyl substituents at the double bond and at the carbinol carbon atom, constitutional relationship between the double bond and the hydroxyl group) there are two possible competing reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and with a more remote double bond) addition occurs; mono- and disubstituted secondary and tertiary Δ⁴- and Δ⁵-alkenols cyclize in high yields to give the corresponding cyclic ethers. Received March 17, 2000. Accepted (revised) May 31, 2000