Rhodium-Catalyzed Reactions of a Vinyldiazoacetate
with N-Substituted Semicyclic Enaminones
Andreas Müller, Andreas Endres and Gerhard Maas*
Institute for Organic Chemistry I, University of Ulm, Albert-Einstein-Allee 11,
D-89081 Ulm, Germany
* Corresponding author: E-mail: gerhard.maas@uni-ulm.de
Abstract
The rhodium-catalyzed reaction of dimethyl 3-diazo-1-propene-1,3-dicarboxylate
(4) with N-substituted five-membered
semicyclic enaminones 1 yields (3-ammoniopropyl)cyclopentadienides 7 and/or
dienamines 8 which formally represent
products of carbenoid insertion into the enaminic β-C–H bond of 1. The thermal
isomerization 8 → 7 is facilitated
by electron-donating substitutents at the N atom and at the carbonyl group of
the enaminone moiety. Thus, N-alkyl
substituted dienamines 8 in general undergo the isomerization, while N-phenyl
substituted analogues do not rearrange.
The isomerization behavior of the
N-methyl-3-(anthracen-9-ylcarbonyl)-substituted dienamine 8c is complex:
isomerization
into betaine 7c is achieved in low yield in the presence of sodium methanolate,
while thermal impact in the presence
of silica gel generates pentacycle 9 as a result of an intramolecular
Diels-Alder reaction at the anthracene moiety.
In complete analogy to the transformation 1→8, the rhodium-catalyzed reaction of
vinyldiazoacetate 4 with the dimedone-derived 3-morpholinocyclohex-2-en-1-one
11 yields the olefinic C–H insertion
product 12.Keywords: Cyclopentadienides, diazo compounds, dienamines, enaminones, rhodium
carbenoids