On the use of boronates in the Petasis reaction

Alcohols are solvents of choice to react boronates, aldehydes and either primary or secondary amines. Thus, while the reaction proceeds sluggishly, or not at all, in aprotic solvents, the desired aminoacids are in most cases obtained in high yields when conducted in methanol or hexafluoro-iso-propanol. In the case of secondary amines, microwave activation is shown to strongly accelerate the process without altering the yields.