A new synthesis of vitamin K viaπ-allyinickel intermediates

Abstract

A new synthesis of vitamins K₁(1), and K_2(5n)(2) is described. Reaction of bis-(1–3-η-3-alkylbut-2-enyl)di-µ-bromodinickel complexes (8a–c) with 2-bromo-3-methylnaphthalene-1,4-diyl bis(methoxymethyl) ether (6a) or diacetate (6b) in a polar, co-ordinating solvent gave the corresponding vitamin K derivatives (9a–d) in high yield, which were converted into vitamin K analogues also in high yield. The stereoselectivity decreases as the donor strength of the solvent increases. All-trans-vitamin K₂₍₄₅₎(2b) was isolated from the trans–cis-mixture (70:30) prepared by this method.