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Reactions of Complex Ligands, LXX . An Intramolecular Alkyne Insertion/Carbonylation/Cyclization Sequence of Chromium Aminocarbene Complexes: A Novel Access to Indole and Indenoindole Skeletons
Author(s) -
Leese Thomas,
Dötz Karl Heinz
Publication year - 1996
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19961290606
Subject(s) - alkyne , chemistry , annulation , carbene , intramolecular force , carbonylation , medicinal chemistry , substituent , alkylation , stereochemistry , chromium , indole test , catalysis , organic chemistry , carbon monoxide
2‐Alkynylanilinocarbene chromium complexes 1–7 bearing a rigid arene C 2 spacer between the aminocarbene and alkyne units were prepared from pentacarbonyl(aroyl)chromates(–I), acetyl bromide, and 2‐alkynylanilines. They undergo intramolecular cyclization the course of which depends on the substitution pattern at the alkyne terminus. A tandem alkyne insertion into the metal–carbene bond/carbonylation sequence affords Cr(CO) 3 ‐coordinated 3‐indolylketenes 8, 9, 12–14 by using a bulky substituent; the rate of the reaction increases with N ‐alkylation. Less bulky n ‐alkynylanilinocarbene complexes 4, 5 exhibit two competing carbene annulation sequences: Benzannulation leads to benzo[ a ]carbazoles 15, 16 , whereas cyclopentannulation without prior carbonylation furnishes indeno[1,2‐ b ]indoles 17, 18 .