Borono-Mannich condensation

Petasis (borono-Mannich) condensation (Scheme 91) [353] To piperazinetrityl resin (32 mg, 0.030 mmol, loading 0.95 mmol g ) weighed out in a 10-mL Teflon fritted vessel was added a solution of glyoxylic acid monohydrate (0.032 mmol) in dry THE (2 mE). The suspension was allowed to mix under N2 at r. t. for 2 h. An excess of DEAM-PS boronic ester (120 mmol) was then added, followed by THP/EtOH 8 3 (v/v) (1.5 mE). The suspension was mixed under N2 at 55 °C for 48 h and then cooled at r.t. The resin mixture was filtered and washed as follows ... 

In 2003, Portlock and coworkers [53a] demonstrated that the Petasis borono Mannich (three-component) condensation can be performed in tandem with the Ugi (four-component) condensation to provide access to six-dimensional libraries of compounds with application in the drug discovery area. 

An inherent advantage of the Petasis borono-Mannich reaction is the ability to conduct reactions in a three-component fashion, since the imine or iminium ion intermediates can be formed in situ from the condensation of either primary or secondary amines with the corresponding aldehydes or ketones. The operational advantages of such a three-component coupling approach, combined with the practical benefits outlined above, render the Petasis borono-Mannich reaction particularly desirable for parallel synthesis applications and in the generation of combinatorial libraries. In-... 

In contrast to its intermolecular counterpart, an intramolecular Borono-Mannich reaction (Petasis condensation) has been found to proceed with exclusive anti stereoselectivity. The aza-Cope/Mannich reaction has been reviewed. Unprecedented nucleophilic tribromomethylation of Al-t-butanesulfinylimines by bro-moform enables the synthesis of enantiomerically pure a-tribromomethyl amines and 2,2-dibromoaziridines. ... 

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