Ring-Chain Tautomerism in 1,3-Oxazines

Article abstract of DOI:10.1021/jo00226a018

A comparative study on the ring-chain tautomerism of 49 2-(substituted-phenyl) tetrahydro-1,3-oxazines of seven different types, namely, tetrahydro-1,3-oxazines 3,r-8a,c-2,c-4a- and r-8a,c-2,t-4a-1,3-perhydrobenzoxazines 5 and 7,r-8a,c-2,c-4- and r-8a,c-2,t-4a-1,3-perhydrobenzoxazines 9 and 11, 3,4-dihydro-2H-1,3-benzoxazines 12, and 1,2-dihydro-4H-3,1-benzoxazines 13, pointed out that in all cases the equilibria can be described with a simple equation, log K_x = (0.76 +/- 0.04)?⁺ + logK_X=H where K_x = /(X<*>/H).A factor c illustrating the sum of ster ic and electronic effects of substituents at C-4,C-5, and C-6 has also been introduced