Petasis Borono-Mannich Reaction Iminium Ions Possessing Neighboring Heteroatom Functionality

Petasis Borono-Mannich Reaction Iminium Ions Possessing Neighboring Heteroatom Functionality 

Reactions of Clyoxylic Acid-derived Iminium Ions 

Boronic esters will also react under appropriate circumstances. Petasis used bis(isopropyl) (2B)-bromoethenylboronic ester in a reaction with glyoicyUc acid and aminodiphenylmethane [34]. Scobie and co-workers have reported the coupbng of pinacolyl aryl and alkenylboronic esters with secondary amines (38). The reaction gave good yields with alkenylboronic esters (70-82%), but worked poorly with aryl-boronic esters (0-12%). In contrast to the above results, the reaction did not proceed with primary amines under the same conditions. 

Microwave acceleration of reactions is a valuable tool for organic synthesis [39], and various specialized instruments are now commercially available. Tye and co-workers have reported the microwave-assisted Petasis borono-Mannich reaction of arylboron-ic acids and primary or secondary amines with either glyoxylic acid or salicylaldehyde [40]. Optimized reaction conditions employed didiloromethane as solvent, and microwave assisted heating at 120 °C for 10 min. Products were obtained in generally modest yields (10-83%), in part due to incomplete reaction conversion imder the reported conditions. 

1 Diastereoselective Addition Reactions to Iminium Ions Derived from Chiral Amines and Clyoxylic Acid 

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