Diastereo- and Enantioselective Synthesis of ∆2-1,2,4-Oxadiazolines by 1,3-Dipolar Cycloaddition of Nitrile Oxides with Chiral Hydrazones
作者:Dieter Enders、Ilka Meyer、Jan Runsink、Gerhard Raabe
DOI:10.3987/com-98-s(h)100
日期:——
Diastereo- and enantioselective 1,3-dipolar cycloadditions of nitrile oxides (3) with alpha,beta-unsaturated hydrazones (2) gave spiro oxadiazolines (4) in good yields and low to excellent diastereomeric excesses (de = 5 - greater than or equal to 98%). Open chain hydrazones (6) afforded 5,5-disubstituted Delta(2)-1,2,4-oxadiazolines (7). A subsequent N-N bond cleavage to remove the chiral auxiliary was achieved with formic acid and gave the oxadiazolines (8) (ee = 0 - 91%).