Convenient Synthesis of N-Benzyl-1,4-dihydropyridines, Cyclohexenones, and Bicyclo[3.3.1]nonan-3-one Derivatives from 1-Aza-1,3-butadienes

Abstract

Readily available 1-aza-1,3-butadienes (enimines) react with methyl acetoacetate and acetylacetone in the presence of catalytic amounts of lithium iodide to form in high yields unsymmetrically substituted 1,4-dihydropyridines or cyclohexenones. The reaction pathway depends on the structure of the enimine used. This divergence was not observed when the enimines were reacted with dimethyl 1,3-acetonedicarboxylate to provide bicyclo[3.3.1]nonane-3-one derivatives in excellent yields in a remarkably stereoselective reaction.

C−C versus C−O Anionic Domino Cycloalkylation of Stabilized Carbanions: Facile One-Pot Stereoselective Preparation of Functionalized Bridged Bicycloalkanones and Cyclic Enol Ethers

“…On the other hand, we observed a good regioselectivity in favor of 4 e (entry 3) arising from a selective C-alkylation at the more accessible C5-position. The expected structure and stereochemistry of 4 e, f were detucted from extensive 1 H and 13 C NMR studies using essentially homonuclear correlations as shown on Figure 6 for compound 4 e. Cycloheptanones 1 g, h also give excellent yields of the corresponding tri-and tetracyclic enol ethers 4 k, l but surprisingly, a significant loss of the trans-selectivity was observed leading to a trans/cis ratio of 17 and 6.5, respectively (entries 8,9).…”

“…[3] However, in spite of the synthetic usefulness of these systems, only few reports deal with the reactivity of readily accessible 1,3-diactivated ketones. [4] In the acyclic version, utilization of commercially available dialkyl 1,3-acetonedicarboxylates has led to interesting transformations by reaction with various dielectrophiles such as 1,3-diacetals, [5] 1,2-dicarbonyls, [6] a-bromomethyl acrylates, [7] 1-aza-1,3-butadienes, [8] a,b-unsaturated aldehydes, [9] bisbromomethyl aromatics, [10, 11a] and other a,w-dihalides. [11b,c] On the other hand, the chemistry of anionic species derived from cyclic 1,3-ketodicarboxylates has found only limited applications.…”

Silica‐supported Perchloric Acid Catalyzed One‐pot Synthesis of 1,4‐Dihydropyridines

“…Because of their biological activities and synthetic point of view few efficient routes have been developed, these are the reaction between α,β-unsaturated imines and β-dicarbonyl compounds in the presence of sodium ethoxide 9 at 150 ℃, Michael reaction followed by cyclization between a β-dicarbonyl compound and α,β-unsaturated imine in the presence of lithium iodide 10 and hetero Diels-Alder reactions of 1-azadienes and allenic esters 11 to generate the N-aryl and C 5 -C 6 -unsubstituted systems. However many of these procedures have one or more disadvantages such as refluxing at high temperature, long reaction times (55-85 h), requiring unusual starting materials, using toxic solvents, forming side products, low yields, and difficulties in workup.…”

Sodium Benzoate as a Mild Base Catalyst for the Tandem Michael-Aldol Self-Condensation of γδ-Unsaturated β-Ketoesters

“…Robinson type annelations) [5,6], and alkylations of enolizable 1,3-cyclohexadiones [7]. Recently, N-tert-butyl-1-aza-1,3-butadienes have been reacted with -diketones to furnish 2-cyclohexenones [8]. One of us has described the synthesis of 2-cyclohexenones via a Michael-Wittig condensation of substituted 2H-pyran-5-carboxylates and the -arsonium ylide of acetoacetate [9] which is based on a similar observation obtained from condensations of conjugated unsaturated carbonyl compounds and the -phosphonium ylide of acetoacetate [10].…”