Transacetalization of diethyl tartrate with acetals of alpha-dicarbonyl compounds: A simple access to a new class of C-2-symmetric auxiliaries and ligands

A simple access to a new class of C-2-symmetric auxiliaries and ligands is based on the transacetalization of diethyl tartrate (1) with monoacetals of butane-2,3-dione in the key step. Acid-catalyzed reaction of 1 with 2 equiv of 3,3-diethoxybutan-2-one (2) gives the C-2-symmetric 1,4-dioxane 7 in 88% yield. Reduction of 7 with LiAlH4 affords the crystalline diol 9. The structure of 7 was established from the X-ray structure of 9. Dioxane 7 was converted by standard methodology into the diphosphine 24 and the TARTROL 22. Reaction of 1 with 3,3-dimethoxybutan-2-one (3) in the presence of BF3-etherate gives in analogy to the formation of 7 the 1,4-dioxane 8. This compound was transformed into the diphosphine 25 and the TARTROL 23. The trans-diaxial relationship of the methoxy groups present in 8 could be deduced without X-ray analysis from the H-1-NMR spectrum of 23.