A Novel Stereocontrolled Synthesis of Cis-Fused Bicyclic Lactams via [3 + 2]-Cycloaddition of Alkynyltungsten Complexes with Tethered Aziridines

Abstract

Treatment of alkynyltungsten complexes with tethered aziridines in the presence of BF(3).Et(2)O led to [3 + 2]-cycloaddition reactions, affording bicyclic tungsten-enamine species stereoselectively. The stereochemistry of the resulting product reveals that ring opening of aziridine is initiated by S(N)2 attack of the tungsten fragment. Decomplexation of these organometallics with I(2) in CH(2)Cl(2), followed by hydrolysis, afforded only cis-fused bicyclic lactams efficiently. [reaction: see text]

Aziridines in Formal [3+2] Cycloadditions: Synthesis of Five‐Membered Heterocycles

“…[18] Scheme 11. All attempts to promote the cyclization with cis-aziridine derivatives failed, leading to a different outcome.…”

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…427, Scheme 41) with Lewis acids was re- ported [508]. This reaction afforded dihydropyrrole derivatives (e.g.…”

4 Heterocyclic chemistry

“…Fused pyrrolidinones have been formed by a [3ϩ2] cycloaddition of alkynyl tungstens with tethered aziridines. 42 The intermediate 2-tungsten-pyrrolines were converted to pyrrolidinones by tungsten-iodine exchange followed by hydrolysis. The stereochemistry of the aziridine controls the stereochemistry of the two ring-junction carbon centres (Scheme 23).…”