Substantial yield increases have been noted in the use of a di-SmI 2 binding ligand for the pinacol coupling of alkyl aldehydes compared to 1+1 complexes of SmI 2 and tetraglyme. High diastereoselectivities of ca. 10+1 are also observed for a-substituted alkyl aldehydes in favour of the (±)-isomers.

The samarium diiodide pinacol coupling of benzaldehyde and cyclohexanecarboxaldehyde in the presence of a variety of polyethylene glycols, including derivatives containing carbohydrates has been studied. Whereas such complexing agents allow for the formation of 1,2‐diols, in the case of benzaldehyde the erythro‐isomer predominates with diastereoselectivities of up to 7:1, while with cyclohexanecarboxaldehyde a stereoselectivity of up to 10:1 was observed but in favor of the threo‐isomer. This divergence in the stereoselectivity of these two aldehydes suggests the presence of two different mechanisms occurring in these pinacol coupling reactions.

No abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.