Allylic nitro compounds denitration

The Knoevnagel reaction of 6-methoxytetralc nediamine followed by the nitro-aldol reach allylic nitro compounds Subsequent group Base catalyzed cyclizadon gives the I by radical denitration fsee Section 7 2 ... 

The difficulty in controlling the regiochemistry during radical-denitration of allylic nitro compounds is well known. The migration of the double bond is a serious problem, as shown in Eq. 7.96. This problem is overcome by a hydride transfer reaction in the presence of a palladium catalyst (Eq. 7.97).140... 

The regiochemical control of Pd-catalyzed hydride transfer reaction is much more effective than that of the radical denitration, as shown in Eq. 7.98. The base-catalyzed reaction of nitroolefins with aldehydes followed by denitration provides a new synthetic method of homoallyl alcohols (Eq. 7.99).140 Exomethylene compounds are obtained by denitration of cyclic allylic nitro compounds with Pd(0), HC02H and Et3N (Eq. 7.100).140b... 

Denitration of ally lie nitro groups " Allylic nitro compounds when com-plexed with Pd(0) are reductively removed by a variety of hydride donors. The regioselectivity of denitration to give 1- or 2-alkenes can be controlled by the choice of ligand and by the hydride donor. Thus reduction by formates gives 1-alkenes, and use of NaBH4 or NaBH,CN favors formation of 2-alkenes. 

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