The diastereofacial selectivity of the addition of various 1‐metalated 1‐heptynes to substituted cyclopentanecarbaldehydes. – The use of 1‐titanated 1‐heptyne for the construction of the alkyl side chain of Prostaglandins

Abstract

AbstractA highly diastereoselective addition of 1‐heptyne to substituted cyclopentanecarbaldehydes is one of the indispensable prerequisites to the construction of the (S)‐3‐hydroxy‐1(E)‐octenyl side chain of prostaglandins by palladium(II)‐catalyzed [3,3]‐sigmatropic rearrangement of allylic acetates. It was found that 1‐titanated 1‐heptynes afford the Cram product at best with a diastereofacial selectivity of 92.5%. The corresponding lithium and magnesium compounds are less diastereoselective.