Carbonyl groups, amino functionalization using

Polyphosphoric acid (PPA) has recently been used for the intramolecular reaction of a properly positioned amino group with the carbonyl group of the lactam function of a pyridazin-3(2//)-one unit as exemplified by the ring closure of 2-(2-aminophenyl)phthalazin-l(2//)-one <2006T10018>. 

Besides enzymes, other chemical promoters have been developed for the Ni C2 bond cleavage of activated (3-lactams under not so drastic acid or basic conditions. To this end, the use of 77-acyl (3-lactams, i.e. 77-Boc (3-lactams, as activated substrates has assumed major importance. The 77-acyl group on the substrate (3-lactam serves not only to activate the (3-lactam carbonyl towards the nucleophile attack, but also to protect the amino function in the resulting (3-amino acid derivative product (for the application of this concept to y- and 8- lactams, see [67]). 

Nitro compounds are also useful starting materials, because a nitro group can be readily converted to a carbonyl group or to amino functionality. Addition reactions of nitroalkane have been reported by Yamaguchi [13b], Shibasald [6a], Bako and Toke, Corey, Hanessian, and Kanemasa [21]. For example, Kanemasa used their chiral Lewis acid complex 35 for the reaction of 36 with nitromethane (Scheme 18). The reaction proceeded with the aid of the amine co-catalyst, affording the product 37 with high enantioselectivity. This system was also applicable to the reaction of malononitrile [2 le]. 

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