New Strategy for the Synthesis of 3,4,5-trisubstituted Isoxazolines from Allyl Compounds

A new strategy for the synthesis of trans-and cis + trans-3,4,5-trisubstituted isoxazolines from allyl compounds of QCH(2)CH=CH2 type (Q = PhO, 2,2'-bithiophen-5-yl, BuO, Me3CS, PhN(COMe) and others) has been developed. The dipolarophiles are prepared via: a) Ru-carbene catalysed metathesis of Qallyl; b) catalytic isomerization followed by Ru-carbene mediated metathesis; c) Ru-carbene catalysed metathesis followed by isomerization. 1,3-dipolar cycloaddition of nitrile oxide to dipolarophiles obtained via route a), b) or c), including high pressure activated reactions leads to 3,4,5-trisubstituted isoxazolines. Quantitative E-stereoselective homometathesis of some QCH(2)CH=CH2 to (E)-QCH(2)CH=CHCH(2)Q and new highly effective ruthenium and basic catalytic systems for the isomerization of allyl compounds have also been presented. Moreover, easily available (Z)-XCH2CH=CHCH2X allyl compounds were used for the synthesis of cis-3,4,5-trisubstituted isoxazolines. It has been proved by in vitro tests that some of the isoxazolines show interesting antifungal activity comparable to that of fluconazole.