2-Substituierte 1,6-Methanol[10]annulene als Dienophile in der [4 + 2]-Cycloaddition mit inversem Elektronenbedarf
作者:U. Reimers、G. Seitz
DOI:10.1002/prac.19933350207
日期:——
The LUMO-diene-controlled [4 + 21 cycloadditions of various at C-2 substituted 1,6-methano [10]annulenes 6, 10 and 13 with the electron-deficient s-cis-fixed diazadiene system of 3,6-bis(trifluoro-methyl)-1,2,4,5-tetrazine (3) are described. With the donor substituted 6 (or its valence tautomer 7) 3 reacts under unusually mild conditions to give the 7,12-methanocyclodeca[d]pyridazine 9 with high site selectivity. The Diels-Alder reaction of 3 with the 2-bromo-1,6-methano[10]annulene (10 half arrow right over half arrow left 11) leads to the 6- and 8-bromo-7,12-methanocyclodeca[d]pyridazines 12 a and 12 b, whereas with the various acceptor substituted species 13 half arrow right over half arrow left 14 the 8-substituted 7,12-methanocyclodeca[d]pyridazines 15 a - c are formed exclusively. Spectroscopic data show, that for all the novel methanocyclodeca[d]pyridazines 9, 12 and 15 the annulenic structure is dominating, but a remarkable reduction of the ring current and a distinct bond alternation is observed compared to the parent 1,6-methano[10]annulene 1.