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The circular dichroism (CD) of in situ formed complexes of steroidal substituted secondary and tertiary alcohols with [Rh2(OCOCF3)4] have been investigated. The applicability of the bulkiness rule, developed for unsubstituted secondary alcohols and connecting the sign of the E band at ca. 350 nm with the absolute stereochemistry of an alcohol, is extended to substituted secondary and tertiary alcohols. The rule works well for secondary and tertiary alcohols containing a double bond, alkoxy, ester or amide groups, halogen substituents as well as additional primary hydroxy groups in a molecule. The influence of other substituents present at the stereogenic center, e.g. a keto-, amino-, azido- or additional hydroxy groups, on CD is also described. It is demonstrated that alcohol molecules bind to the Rh-core at axial positions to form 1:2 adducts of the general formula [Rh2(OCOCF3)4(alcohol)2]. |
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