Oxirane I, prepd. by epoxidn. of (EtO)2CHCH2CH:CH2, reacted with Grignard reagents in the presence of catalytic CuBr to give 78-92% b-hydroxyacetals (EtO)2CHCH2CHR1OH [II; R1 = CH2CMe3, CH2CHMeEt, pentyl, CH2CH2CMe:CH2, CH2Ph, CH2CH2Ph, (CH2)7OR2; R2 = tetrahydropyranyl, SiMe3], which gave enals HCOCH:CHR1 in 50-85% yield on hydrolysis. Careful hydrolysis of II (R1 = CH2CMe3) gave HCOCH2CHR1OH, which formed H2C:CHCH2CHR1OH on Wittig reaction or dimerized to form 1,3-dioxane III. [on SciFinder (R)]