308289-02-3Relevant articles and documents
Novel Me3Si-mediated intramolecular cyclisation/[4 + 2] cyclofragmentation of β-substituted γ-nitro ketones
Tishkov, Alexander A.,Lyapkalo, Il'ya M.,Kozincev, Anton V.,Ioffe, Sema L.,Strelenko, Yuri A.,Tartakovsky, Vladimir A.
, p. 3229 - 3233 (2000)
5-Nitro-4-phenylpentan-2-one (1) was found to undergo hitherto unknown Me3SiBr/Et3N-promoted cyclisation into the intermediate six-membered cyclic nitronate 5. Subsequent silylation of 5 led to the corresponding 2-trimethylsilyloxy-2H-[1,2]oxazine C, which undergoes a facile [4 + 2] cyclofragmentation to give 2-phenylpropenal oxime trimethylsilyl ether (6) in moderate yield. The intermediacy of the open-chain trimethylsilyl nitronate 2 and the cyclic nitronate 5 was confirmed by independent experiments. The transformation of the bicyclic nitronate 8 into the 8-trimethylsilyl-oxyimino-7-phenyloct-6-enoic acid trimethylsilyl ester (9) upon silylation proved the silylation/cycloreversion to be a key step in 1,3-azadiene moiety formation. The presented sequence of reactions could be carried out in one pot in low yield by a Me3SiOTf/Et3N-promoted hetero-[4 + 2] cycloaddition of 2-(trimethylsilyloxy)propene to (E)-2-nitro-1-phenyl-ethene, followed by silylation and fragmentation of the intermediate C.
