Henry Viols

Reactivity of phenyllithium toward bridgehead nitrogen heterocycles

The reactivity of phenyllithium toward some bridgehead nitrogen heterocycles was investigated. Imidazo[1,2-a]pyridine gave the substitution, while other series gave addition reactions. In addition, the ring opening derivative was obtained in imidazo[1,2-c]quinazoline series

Cyclisation reactions of some 3-nitrosoimidazo[1,2-a]-pyridines and-pyrimidines. Ring-opening/ring-closure reactions with triethyl phosphite: reassignment by X-ray crystal structure and nuclear magnetic resonance

Deoxygenation of 3-nitroso-2-phenylimidazo[1,2-a]-pyridines and -pyrimidines with triethyl phosphite does not lead to the products described in the literature as pyrido- and pyrimido-imidazoindoles (3) and (4), but to the open-chain derivatives, N-(2-pyridyl)- and N-(2-pyrimidyl)-benzimidoyl cyanides (5) and (6). X-Ray crystallographic analysis confirms the structure of (5a): orthorhombic system with a= 24.377 (6), b= 11.729 (3), c= 7.534 (2)A, space group Pbca, Z= 8, d= 1.27 g/cm3, R= 0.061. Thermal ring-closure with triethyl phosphite of compounds (5) and (6) produced the 3-amino-2-phenylimidazo[1,2-a]-pyridines and -pyrimidines (8) and (9).

PREPARATION AND REACTIVITY OF 1-BENZYL-2,4-PIPERIDINEDIONE-3-CARBOXYLIC ACID DERIVATIVES

The preparation and structural determination of 2,4piperidinedione-3-carboxylic acid methyl ester 4. by a Dieckmann reaction was reported. Decarbomethoxylation and alkylation studies on A were also reported. The 4-piperidone framework has been used as synthetic intermediates specially in the synthesis of natural products and compounds with pharmacological interest (1), while synthetic applications of 2,4piperidinedione derivatives have been reported in the preparation of emetine-like antiepileptic, herbicide agents (2) and patented, for examples as therapeutic agents for liver disorders (3) . As a part of our program on the reactivity of heterocycles, we are now interested in the study of the reactivity of 2,4-piperidinedione-3-carboxylic acid ester. Methyl N-Benzyl-ß-alaninate 1 was obtained admixed with the tertiary amine 2 by Michael addition of methyl acrylate on benzylamine (52:38% yield respectively) in a mixture of methanol, water and triethylamine, according the procedure of Christie and Rapoport (4) . Finally, 1 was obtained in 86% yield in ethanol according the procedure of Huizenga and Pandit (5) . Compound 1 reacts with methyl malonyl chloride in dichloromethane-water in presence of potassium carbonate to give the amide 2 with 92% yield (6). The lH and 13C-NMR spectra were more complex due to the presence of two rotamers in the 60:40 ratio. In the case of acyclic amide, it was well established that the groupment in trans from the carbonyl resonate at a lower field Vol. 4, No. 4, 1998 Preparation and reactivity of l-benzyI-2,4-piperidinedione-3-carboxylic acid derivatives than the cis (7) . These results, in good agreement with the anisotropy diamagnetic model of amide described by Paulsen and Todt (8) led to the following assignments.