FORMATION OF 6,6-DIMETHYL-2,4-CYCLOHEXADIENYLIDENE-1-IMINES FROM PRIMARY AMINES AND 2,6-DIISOPROPYLPYRYLIUM SALTS

Article abstract of DOI:10.1016/S0040-4039(00)96306-8

2,6-Diisopropyl-substituted pyrylium salts 5 react with primary amines RNH2 yielding pyridinium salts, 6, and 6,6-dimethyl-2,4-cyclohexadienylidene-1-iminium salts, 7, in relative amounts depending on the group R (100/0 for R=Me, 93/7 for R=Et, 20/80 for R=iPr, and 0/0 for R=tBu) proving that steric factors are as important as aromatic delocalisation in ANRORC reactions of pyrylium salts.