Sulphinyl compounds rearrangement

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... 

Reaction of the carbanion of chloromethyl phenyl sulphoxide 409 with carbonyl compounds yields the corresponding 0-hydroxy adducts 410 in 68-79% yield. Each of these compounds appears to be a single isomer (equation 242). Treatment of adducts 410 with dilute potassium hydroxide in methanol at room temperature gives the epoxy sulphoxides 411 (equation 243). The ease of this intramolecular displacement of chloride ion contrasts with a great difficulty in displacing chloride ion from chloromethyl phenyl sulphoxide by external nucleophiles . When chloromethyl methyl sulphoxide 412 is reacted with unsymmetrical ketones in the presence of potassium tcrt-butoxide in tert-butanol oxiranes are directly formed as a mixture of diastereoisomers (equation 244). a-Sulphinyl epoxides 413 rearrange to a-sulphinyl aldehydes 414 or ketones, which can be transformed by elimination of sulphenic acid into a, 8-unsaturated aldehydes or ketones (equation 245). The lithium salts (410a) of a-chloro-/ -hydroxyalkyl... 

The first general method of transforming a penicillin into a cephalosporin, the acid-catalysed rearrangement of penicillin sulphoxides, continues to receive attention. That this rearrangement proceeds via a sulphenic acid derivative has been further confirmed by isolation of the crystalline sulphenic acid (74 f, y) from the thermal rearrangement of the penicillin sulphoxide (27 f, y). This intermediate slowly reverts to the penicillin at 38 0, and, on treatment with methanesulphonic acid in dimethylacetamide, cyclizes to cephalosporin (75 f, y). Trapping of (74) by oxidation to the sulphinyl chloride (76 f, y) has been reported cyclization to a cephalosporin sulphoxide was accomplished under base catalysis/ Treatment of penicillin sulphoxides with azo-compounds also effects rearrangement to... 

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