Weinreb amides (N-alkoxy-N-methylamides), WA hereafter, provide a very convenient synthesis to aldehydes and ketones.
The collapse of the intermediate usually requires aqueous work up, which avoids over-addition despite the use of a large excess of reagents.
WA are very attrractive since they are easy to prepare, are very effective, reactions are scalable and provide stability-storability. The facile reduction to aldehydes with hydride reduction agents makes them serve as precursor to sensitive aldehyde in the masked form.
When treated with reagents as Lithium DiisoprPropylAmine at low temperatures results in demethoxylation with concomitant release of formaldehyde. This undesired competitive pathway can be overcame by using a t-butoxy group instead of a methoxy.
No comments:
Post a Comment