✍ Scribed by Prof. Dr. Reinhard W. Hoffmann
No coin nor oath required. For personal study only.
In an ideal synthesis, the formation of the CC bonds as well as the creation of the chiral centers and of the final functionality would be carried out simultaneously in each step. Accordingly, stereoselective CC bond forming reactions are required. Instead of a pair of diastereomers, a synthesis should yield only one of the two possible diastereomers. Such selectivity is often achieved in the addition of crotylboron, ‐aluminum, ‐tin, ‐titanium, and ‐chromium compounds to aldehydes. Depending on whether one starts from E‐ or Z‐crotyl compounds, one diastereomeric adduct is formed preferentially. In this case the newly formed CC bond carries a methyl substituent. However, the synthetic goal is often a compound carrying an oxygen function at the site of the new CC bond. Compounds of this type can be obtained through addition of heteroatom‐substituted allylboronic acid esters or analogous reagents to aldehydes.
📜 SIMILAR VOLUMES
The poorly reactive 2,2,2 trifluorodiazoethane is able to add to unactivated aldehydes provided that the reaction is performed in presence of Lewis acids. This condensation leads mainly to homologated ketones and aldehydes a substituted by a trifluoromethyl group. 1) Lewis acid 0 CF3CHN2 + RCHO .