Annulation Tactics of cis‐syn‐cis Triquinanes by Allylsilanes: Application of Hosomi‐Sakurai Reaction Conditions

Abstract

A stereoselective [3 + 2] cycloaddition approach to functionalized pentaquinanes starting from cis-syn-cis triquinanes, derived from Cookson's diones, is reported. This transformation involves generation of six new stereocenters in a single step leading to cis-anti-cis-syn-cis-anti-cis poly-quinane systems. Our method prevents transannular cyclizations which are prevalent in these moieties. The structure and stereochemistry of target molecules are well-characterized based on NMR data and X-ray diffraction studies.

Selectivity: A Goal for Synthetic Economy

“…When the same triquinane 104 was treated with allyltriisopropylsilane, instead of allyltrimethylsilane, the pentaquinane 105 was obtained (Scheme 21). 30 Scheme 21 Conjugate addition and cyclopentannulation of triquinane 104 using allylsilanes By changing the brominating reagent, the mono and dibromination of compound 108 was achieved. These monoand dibromo compounds were subsequently employed as useful precursors for fragmentation methodology (Scheme 22).…”