Aliphatic compounds, readily available Table

The yields of the dimeric nitroso compounds are good. Thus the aliphatic nitroso compounds which previously were difficult to obtain become readily available. A series of dimeric nitroso compounds with primary and secondary alkyl groups are given in Table III. 

This method for preparing 2-phenyl-1-pyrroline, and assorted 2-substituted 1-pyrrolines, is one of the best currently available, particularly because it reproducibly affords clean materials. Generally, the procedure is amenable to various aromatic esters 2 it has also been applied successfully to aliphatic esters (Table I).3 An advantage of this method is the use of readily available, inexpensive N-vinyl-pyrrolidin-2-one as a key starting material. This compound serves effectively as a 3-aminopropyl carbanion equivalent. The method illustrated in this procedure has been extended to include the synthesis of 2,3-disubstituted pyrrolines. Thus, alkylation of the enolate of the intermediate keto lactam, followed by hydrolysis, leads to various disubstituted pyrrolines in good yields (see Table II).3... 

One type of oligoamide that can readily be prepared on supports without the need for any partially protected monomers (which are often tedious and expensive to synthesize) are N-substituted oligoglycines (Figure 16.21). These compounds are prepared by a sequence of acylation of a support-bound amine with bromoacetic acid, displacement of the bromide with a primary aliphatic or aromatic amine, and repeated acylation with bromoacetic acid. Because primary amines are cheap and available in large number, this approach enables the cost-efficient production of large, diverse compound libraries. Alternatively, protected N-substituted glycines can also be prepared in solution and then assembled on insoluble supports (Entry 5, Table 16.2). 

Building upon an early observation that a-oxonitriles readily react with imines to form the corresponding N-acylamino nitriles [26-28], List devised an asymmetric organocatalyzed acetylcyanation variant (Table 30.5) [29, 30]. Acetyl cyanide is commercially available and, as a Uquid, is convenient to use. In addition, the use of acetyl cyanide makes further derivatization of the hydrocyanation compounds with, for example, TFAA obsolete. Using catalyst 30, the reaction gave high enan-tioselectivities and high yields with aromatic, aliphatic, heteroaromatic, aUphatic-branched and -unbranched, and unsaturated imines. 

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