Sulphinates alkynyl

The iodonium triflate (460 mg, 1 mmol) was added to a stirred slurry of anhydrous sodium p-toluene sulphinate (180 mg, 1.01 mmol) in dichloromethane (15 ml) at 20°C under nitrogen. After 15 min water (10 ml) was added and the phases were separated the aqueous layer was extracted with additional dichloromethane (2 x 5 ml), and the combined organic extracts were dried. The filtered solution was treated with hexanes (30 ml) and concentrated. The solid residue was purified by radial chromatography (silica gel, 200-400 mesh, dichloromethane-hexanes) to afford 3-tosyl-bicyclo[3.2.0]-3-heptene-2-one (197 mg, 75%), m.p. 164-165°C. The method is general for the preparation of sulphones with a cyclopentenone moiety other alkenyl iodonium salts gave alkynyl sulphones with sulphinates (Section 9.4.4). 

In view of their importance in asymmetric synthesis new routes have been developed to chiral sulphoxides and related species. Sulphinates, useful as precursors of chiral sulphoxides, have been prepared in 40-70% enantiomeric excess and the synthesis and dieno-philic properties of the isomeric sulphinyl acrylates (2l8) and (219) (Ar = 4-MeCgH ) have been described. ( )-Vinyl sulphoxides have been prepared in high optical purity via 1-alkynyl... 

N.m.r. and i.r. spectroscopy, and chemical evidence, all suggest that the mechanism of insertion of sulphur dioxide into metal-carbon bonds in such compounds as Fe(A -C6H6)(R)(CO)2, Mo(A -C6H6)(R)(CO)3, and MnR(CO)6 involves initial formation of an O-bonded sulphinate, e.g. (23), followed by rearrangement to the stable S-bonded product, e.g. (24). The reaction of sulphur dioxide with 2-alkynyl compounds of transition metals was first considered to produce allenyl(oxy)sulphinyl compounds MS(0) 0C(R)=C=CH2. Later, the products were said to be allenyl-O-sulphinates, MOS(0) C(R)=C=CHa. Now the available evidence... 

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