Spiro fused β-lactam cyclopropenes

Abstract

. A3-1 ,3,4-Oxadiazolines (I) that share their C2 with C4 of a p-lactam ring in a spiro fusion were repared. The struc-P tures were established through single crystal X-ray diffraction of l a and by infrared, 'H, and C nuclear magnetic resonance spectroscopies. Thermolysis of 1 at 100°C, in benzene containing dimethyl acetylenedicarboxylate, afforded spiro-fused p-lactam cyclopropene 12 in 33% yield. Similar thermolysis of l b in the presence of ethyl phenylpropiolate gave spiro-fused p-lactam cyclopropene 13 (32%). The molecular structure of 12, determined by single 5rystal X-ray diffraction, has the two ester carbonyl carbons out of the plane of the cyclopropene ring by about 0.17 A, indicating substantial nonbonded steric interactions and suggesting unusually high strain energy. At 154.5"C, 12 underwent isomerization to 19, presumably through a vinyl carbene intermediate. [Traduit par la rCdaction]

Thermally Induced Cyclopropene−Carbene Rearrangements: An Overview

“…The bicyclic cyclopropene 171 carrying a 3-amide substituent rearranges in benzene in 4 h at 154 °C in a sealed tube, giving a low yield of 172 , apparently derived by intramolecular trapping of a vinylcarbene:

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Isolation and structure determination of the first example of the azeto[2,3-c]quinolizinedione ring system

“…Other pathways to give 9 can be conceived, and the mechanism of the reaction is under further investigation. Very few examples of compounds in which a β-lactam ring is fused to an otherwise unsaturated naphthalene type ring are known, [14][15][16][17] and, to the best of our knowledge, none to an unsaturated heterocyclic framework. Compounds of type 9 are likely to exhibit useful biological activity, and further work to improve the yield and scope of this reaction is in progress.…”