Yuzuru Uchida

Formation of 2,2′-bipyridyl by ligand coupling on the phosphorus atom

Abstract Phosphonium salts and phosphine oxides, bearing at least two 2-pyridyl or substituted 2-pyridyl groups gave the corresponding 2,2′-bipyridyls and pyridines upon treatment with acid or neutral solvents such as water and alcohols, in substantial yields.

Ligand coupling reaction on the phosphorus atom

Abstract Phosphine oxides bearing two or three 2-pyridyl groups were found to react with organometallic compounds affording 2,2′-bipyridyl, 2-substituted pyridines and pyridine in substantial yields. Both ligand exchange and ligand coupling appear to take place within the penta-coordinated phosphorus intermediates formed incipiently.

Unusual formation of 5-halo-2,2′-bipyridyls by treatment of tris(2-pyridyl)phosphine derivatives with halogens

Abstract Reaction of tris(2-pyridyl)phosphine with chlorine in dichloromethane or acetonitrile gave chlorotris(2-pyridyl)phosphonium chloride which afforded a coupling product, 2,2′-bipyridyl, by treating with dilute HCl. Treatment of tris(2-pyridyl)phosphine or tris(2-pyridyl)phosphine oxide with chlorine or bromine in methanol gave unusual 5-halo-2,2′-bipyridyl as a major coupling product. This is undoubedly an electrophilic substitution on a pyridyl ring in the pentacovalent phosphorane.

Preparation of 5-Halo-2,2′-Bipyridyls

Abstract Earlier, we have shown that treatment of tris(2-pyridyl)phosphine1) or tris(2-pyridy1)phosphine oxide2 with 2-pyridyllithium resulted in the formation of ligand coupling products, namely 2,2′-bipyridyl, as shown below.

A novel route to 2-substituted 1,2-benzisothiazol-3(2H)-ones

2-Alkyl- and 2-aryl-1,2-benzisothiazol-3 (2H)-ones were synthesized in high yields by the cyclization of 2-(methylsulphinyl)benzamides with thionyl chloride.

Electrophilic Substitutions on Tris(Pyridyl)Phosphine

Eversince Seyferth ran the very odd reaction which he dit not add any word, this has remained as the first example of stereochemistry of phosphorus atom centered ligand coupling reaction in the hypervalent species and the reaction is the following.(1)