7- Azabicyclo hepte-2,5-dienes

Azabicyclo[4.1.0]hept-3-enes, e. g. 13, are available from 1,4-dihydrobenzenes 12 by the route indicated, and are useful precursors for the synthesis of specifically substituted 1//-azepines free from isomeric contamination.61 For example, low temperature addition of bromine to bicycle 13 yields the dibromo derivative 14 which, with powdered sodium methoxide in tet-rahydrofuran, undergoes a double dehydrobromination followed by electrocyclic ring opening of the resulting 7-azabicyclo[4.1.0]hepta-2,4-diene 15 to give methyl l//-azepine-l-carboxylate (16). 

The structure of the product obtained by the silver(I) ion catalyzed ring expansion of anti-1-chloro-2,3-benzo-7-azabicyclo[2.2.l]hepta-2,5-diene, formulated tentatively as 1-methoxy-l/f-1-benzazepine,140 has been shown to be 2-methoxy-6,7-benzo-l-azabicyclo[3.2.0]hept-3-ene... 

Chemistry of 7-azabicyclo[2.2.1]hepta-2,5-dienes, 7-azabicyclo[2.2.1]hept-2-enes and 7-azabicyclo[2.2.1]heptanes , Chen, Z. and Trudell, M. L.,... 

The discovery of the structure of 7-azabicyclo[2.2.2]heptene isolated from the Ecuadorian poison frog, Epipedobates tricolor [39], has caused a rebirth of investigation of Diels-Alder reactions with pyrrole as a diene [40]. Subsequently, a large number of 7-azabicyclo[2.2.1]-heptane and 7-azabicyclo[2.2.1]hept-2-ene derivatives have been synthesized and protected by patents [41]. We have... 

Labile N-nitrosamines. A soln. of NOCl in CCI4 added at -10 to -15° to a mixture of 2,3-benzo-7-azabicyclo [2.2.1] hepta-2,5-diene and Na-acetate in the same solvent, and stirring continued 5 min. at -10° - 7-nitroso-2,3-benzo-7-azabicyclo[2.2.1]hepta-2,5-diene. Y 44%. — The stable 7-nitroso-2,3-benzo-7-azabicyclo [2.2.1] hept-2-ene is similarly obtained in 83% yield. L. A. Carpino and D. E. Barr, J. Org. Chem. 31, 764 (1966). 

A review of formal aza-Diels-Alder reactions of imines with e-rich dienes and enones, in the presence of Lewis acids/Brpnsted acids/organocatalysts, has been presented. Bifunctional A-acyl aminophosphine catalysts (75) are effective asymmetric organocatalysts in the hetero-4- -2-cycloaddition of a-substituted allenoates with tosylaldimines to produce optically active tetrahydropyridines. The Brpnsted acid-catalysed aza-Diels-Alder reactions of cyclopentadiene with iminoacetates possessing two chiral auxiliaries yielded 2-azabicyclo[2.2.1]hept-5-ene cycloadducts with high exo-selectivities. ... 

The nickel-iminophosphine-catalysed 4- -2-cycloaddition of enones with allenes formed highly substituted dihydropyrans. The enantioselective amine-catalysed 4-I-2-cycloaddition of allenoates with oxo-dienes produced polysubstituted dihydropyrans in high yields and with high enantioselectivities. Novel enam-ine/metal Lewis acid bifunctional catalysis has been used in the asymmetric inverse-electron-demand hetero-Diels—Alder reactions of cyclic ketones with Q ,j9-unsaturated a-ketoesters. The 4- -2-cycloaddition of acylketenes (80) with 2-unsubstituted and 2-monosubstituted 3-aryl-2//-azirines (81) produced 1 1 (82) or 2 1 (83) adducts, being derivatives of 5-oxa-l-azabicyclo[4.1.0]hept-3-ene or 5,7-dioxa-l-azabicyclo[4.4.1]undeca-3,8-diene. The formation of the monoadducts proceeds via a stepwise non-pericyclic mechanism (Scheme 25). A-heterocyclic carbene-catalysed 4- -2-cycloaddition of ketenes with 1-azadienes yielded optically active 3,4-dihydropyrimidin-2-ones (93% ee) ... 

Wang discovered that the imino Diels-Alder reaction of simple aldeltydes, amine hydrochlorides and dienes, initially reported by Grieco, could be performed in water in the pH range of 5-7 in the presenee of lanthanide inflates as Lewis acid catalysts to obtain 2-benzyl-3-ethyl-2-azabicyclo[2.2.1]hept-5-ene derivatives 52 [38] (Scheme 1.25). 

A soln. of tosyl cyanide in cyclopentadiene allowed to stand 0.5 hr. at room temp. -> 3-tosyl-2-azabicyclo[2.2.1.]hepta-2,5-diene (Y 95%) dissolved in acetic acid, then ice-water added -> 2-azabicyclo[2.2.1]hept-5-en-3-one (Y 64%). F. ring closures s. J. C. Jagt and A. M. van Leusen, J. Org. Chem. 39, 565 (1974). 

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