B. Tinant, J. Feneau-Dupont, J. Declercq
1992
Citations
0
Influential Citations
8
Citations
Journal
Journal of The Chemical Society-perkin Transactions 1
Abstract
4-Cyano-1-methyl-1,2-dihydropyridine 1 is a highly activated captodative diene known to cyclodimerize, even at -45-degrees-C, in a [2 + 2] mode to 2 which isomerizes above -20-degrees-C to the [4 + 2] dimer 3. Compound 3 is now found to equilibrate above approximately 50-degrees-C with the monomer 1. In addition 3 furnishes, with dimethyl acetylenedicarboxylate in boiling acetone, the expected [2 + 2] adduct 7 along with the title compound, a surprising 2:1 adduct 6 of dimethyl acetylenedicarboxylate and 1. Both new structures 6 and 7 are proven by X-ray analysis. The crystals of 6 (C19H20N2O8) are monoclinic, space group P2(1)/n, Z = 4, with a = 13.818(2), b = 10.994(2), c = 13.128(2) angstrom, beta = 100.00(1)-degrees, V = 1963.4(5) angstrom3. Using 2754 independent reflections with I greater-than-or-equal-to 2.5sigma-(I) the structure was refined to R = 0.054. The crystals of 7 (C20H22N4O4) are also monoclinic, space group P2(1)/c, Z = 8, with a = 20.229(7), b = 11.307(3), c = 18.199(4) angstrom, beta = 103.73(2)-degrees, V = 4044(2) angstrom3. This second structure was refined to R = 0.058 using 2718 observed reflections.