TY - JOUR
T1 - The Synthesis of Carbazoles from 3-Vinylindoles with Tetracyanoethylene and Dimethyl Acetylenedicarboxylate
AU - Noland, Wayland E
AU - Kuryla, William C.
AU - Lange, Ronald F.
PY - 1959
Y1 - 1959
N2 - The tricyanovinylation of indole has been extended to substituted indoles, including 1-methylindole, 2-methylindole and 1,2-dimethylindole, giving the corresponding 3-tricyanovinylindoles (Ib-Id) in good yields. Several derivatives of the latter are described. Tricyanovinylation of skatole occurred in the 1-position, giving 3-methyl-1-tricyanovinylindole (Ie) in 77% yield. 3-Tricyanovinylindole (Ia) and l-methyl-3-tricyanovinylindole (Ib), acting as dienes, undergo Diels-Alder reactions with dimethyl acetylenedicarboxylate, resulting in the loss of hydrogen cyanide and forming the corresponding dimethyl 3,4-dicyanocarbazole-l,2-dicarboxylates (X). Saponification of the latter, followed by esterification of the resulting tetraacids with diazomethane, yielded the corresponding tetramethyl carbazole-l,2,3,4-tetracarboxylates (XI). The one derived from indole (XIa) was prepared independently, along with three minor products CXVIII-XX), by the reaction of indole with dimethyl acetylenedicarboxylate in 1:2 molar ratio. The latter reaction probably involves an intermediate 3-vinylindole (XII) which acts as a diene in a Diels-Alder reaction with a second molecule of dimethyl acetylenedicarboxylate. These reactions appear to represent the_ first examples of the 3-vinylindole synthesis of carbazoles. Decarboxylation of the carbazole tetraacids by pyrolysis with soda-lime gave carbazole in both cases, N-demethylation having occurred in the N-methyl case. Since N-methylcarbazole does not demethylate under the same conditions, it is suggested that the N-demethylation occurs by intramolecular nucleophilic displacement (in a 6-membered ring transition state) of the methyl group by the neighboring 1-carboxylate anion.
AB - The tricyanovinylation of indole has been extended to substituted indoles, including 1-methylindole, 2-methylindole and 1,2-dimethylindole, giving the corresponding 3-tricyanovinylindoles (Ib-Id) in good yields. Several derivatives of the latter are described. Tricyanovinylation of skatole occurred in the 1-position, giving 3-methyl-1-tricyanovinylindole (Ie) in 77% yield. 3-Tricyanovinylindole (Ia) and l-methyl-3-tricyanovinylindole (Ib), acting as dienes, undergo Diels-Alder reactions with dimethyl acetylenedicarboxylate, resulting in the loss of hydrogen cyanide and forming the corresponding dimethyl 3,4-dicyanocarbazole-l,2-dicarboxylates (X). Saponification of the latter, followed by esterification of the resulting tetraacids with diazomethane, yielded the corresponding tetramethyl carbazole-l,2,3,4-tetracarboxylates (XI). The one derived from indole (XIa) was prepared independently, along with three minor products CXVIII-XX), by the reaction of indole with dimethyl acetylenedicarboxylate in 1:2 molar ratio. The latter reaction probably involves an intermediate 3-vinylindole (XII) which acts as a diene in a Diels-Alder reaction with a second molecule of dimethyl acetylenedicarboxylate. These reactions appear to represent the_ first examples of the 3-vinylindole synthesis of carbazoles. Decarboxylation of the carbazole tetraacids by pyrolysis with soda-lime gave carbazole in both cases, N-demethylation having occurred in the N-methyl case. Since N-methylcarbazole does not demethylate under the same conditions, it is suggested that the N-demethylation occurs by intramolecular nucleophilic displacement (in a 6-membered ring transition state) of the methyl group by the neighboring 1-carboxylate anion.
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U2 - 10.1021/ja01531a039
DO - 10.1021/ja01531a039
M3 - Article
AN - SCOPUS:0000906575
SN - 0002-7863
VL - 81
SP - 6010
EP - 6017
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 22
ER -