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Haloalkanesulfonyl bromides including chloromethanesulfonyl bromide (1), bromomethanesulfonyl bromide (2), -bromoethanesulfonyl bromide (3), and iodomethanesulfonyl bromide (4) undergo free radical addition to olefins giving adducts which upon treatment with base afford dienes by a process termed the vinylogous Ramberg-Backlund reaction. In appropriate cases regioselectivity and/or stereoselectivity is observed in both the first addition step and in subsequent base-promoted elimination steps. Using this twoor three-step procedure, 1-alkenes are converted into 1,3-alkadienes, 2-methyl-1-alkenes into 2-alkyl-1,3-butadienes, methylenecycloalkanes into 1-vinyl-1-cycloalkenes, cycloalkenes into 3-methylene-1 -cycloalkenes, and 1 -methylcycloalkenes into 1,2-dimethylenecycloalkanes among other examples. Reagents 1-4 can also be used to convert trimethylsilyl enol ethers into -alkylidene ketones and 1,3-oxathiole 3,3-dioxides, 1,3-dienes into 1,3,5-trienes, and alkynes

ChemInform Abstract The title compound (IV) is prepared in two steps from the trans ethene (I). Oxidation of (IV) yields the S-oxide (V), which is found to be remarkably stable for a sulfoxide with a silyl group syn to the oxygen. Heating of (V) with the acetylenedicarboxylate (VI) affords the thiophenes (VII) and (VIII) by a novel mechanism. In order to obtain information on the magnitude and geometric dependence of the silicon β-effect in radical cations, the ultraviolet photoelectron spectrum of (IV) is determined and compared with the spectra of a series of related silylated or tert.-butyl-substituted thiiranes and oxiranes and their acyclic analogues.

In a study of disulfide-sulfinates containing prolylthio moieties epimeric at C-4, the OH group of N-acetylated 4(R)-hydroxy-2(S)-pyrrolidinecarboxylic acid ("írans-4-hydroxy-L-proline", 3) was converted to an epimeric SH group (11) by replacing a 4-O-tosyl group with PhCH2S (to give 5) and debenzylating. Reaction of 11 as the disodium salt with 1,2-dithiane 1,1-dioxide (2) replaced the H of the SH with S(CH2)4S02Na to give a disulfide-sulfinate salt (9). Since 9 was unstable in solution, with conversion of disodium 4,4'-trithiobis(butanesulfinate) (22) to the diester 23 as a model, 9 was converted to the disulfide-sulfinic ester 10. Subsidiary peaks in the 13C NMR spectra of N-acetyl derivatives were shown to originate from rotamers. Similarly, the epimeric 4(S)-hydroxyproline ( 16) was converted to the 4(R)-mercaptoproline epimer (19) of 11, which was converted in turn to the disulfide-sulfinate epimer (21) of the sulfinic ester 10. The two disulfide-sulfinate esters 10 and 21 were stable under ambient conditions and began to disproportionate to the two symmetrical disulfides in refluxing ethyl acetate in 1.5 (21) toca. 7 h (10). The sulfinic esters 10,21, and 23 seem likely to serve as biological precursors of sulfinate and thiolate salts, which may be useful for several purposes.

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