Abstract
Several γ,δ-unsaturated β-diketones were prepared by acylation of the lithium enolates of cyclic ketones by cinnamoyl chlorides. Reaction of the cinnamoylcyclohexanones with 2 equivalents of hydrazoic acid in sulfuric acid gave bicyclic lactams in good yields. The mechanism of this process involves a Schmidt reaction, followed by addition of HN3 to the enone, migration of the aryl group onto nitrogen, and a cyclisation in which the arylamino group is displaced by the amide nitrogen. The scope of the reaction is limited to the preparation of 7-5 bicyclic systems from enoyl cyclohexanones, other precursors gave dihydropyrones or complex mixtures.
Highlights
The reaction of carbonyl compounds with hydrazoic acid, known as the Schmidt reaction, is a convenient method for the synthesis of a wide variety of nitrogen containing materials.[1]
A notable development, that greatly extends the power of the reaction, has been the discovery that the intramolecular Schmidt reaction of organic azides with ketones (Scheme 1),[3] or with carbocations derived from alkenes or alcohols,[4] can give a wide range of bicyclic products bearing nitrogen at one of the ring fusion positions
We report that reaction of α,β-unsaturated 1,3-diketones, such as 3, with hydrazoic acid produces bicyclic lactams via an unexpected sequence of reactions that includes two Schmidt processes
Summary
The reaction of carbonyl compounds with hydrazoic acid, known as the Schmidt reaction, is a convenient method for the synthesis of a wide variety of nitrogen containing materials.[1]. The reaction of cyclic ketones to give lactams is a useful application, and many examples are known In recent times, this method has been extended to provide access to some N-substituted lactams by replacing hydrazoic acid with organic azides.[2] A notable development, that greatly extends the power of the reaction, has been the discovery that the intramolecular Schmidt reaction of organic azides with ketones (Scheme 1),[3] or with carbocations derived from alkenes or alcohols,[4] can give a wide range of bicyclic products bearing nitrogen at one of the ring fusion positions. We report that reaction of α,β-unsaturated 1,3-diketones, such as 3, with hydrazoic acid produces bicyclic lactams via an unexpected sequence of reactions that includes two Schmidt processes
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