A new method for the synthesis of mixed orthoesters from O-allyl acetals

摘要

Two new methods for the synthesis of orthoesters and compounds containing an orthoester moiety (dihydroisoxazoles) are presented. Mixed orthoesters of general formulas RC(OR~1)(OR~)2 and RC(OR~1)-(OR~2)(OR~3) were prepared via addition of ROH (R = Bu or m-methylphenyl) to O-allyl acetals (acrolein acetals: diethyl or cyclic, i.e., 2-vinyl-1,3-dioxanes or dioxolanes). The catalytic systems for these reactions were generated from [RuCl2(PPh3)3] and Na2CO3; {[RuCl2(COD)]x} or {[OsCl2(1,5-COD)]_x}, PPh3, and Na2CO3. Compounds containing an orthoester moiety (dihydroisoxazoles) were prepared via tandem isomerization of O-allyl acetals (to O-vinyl acetals) catalyzed by ruthenium complexes followed by cyclo-addition to in situ-generated 2,6-dichlorophenylnitrile oxide.