Cyclopentenyl sulfones

When y-CH bonds are present in the R group of the alkynyliodonium ion, cyclopentenyl sulfones predominate. For example, the treatment of 5-phenyl-1-pentynyl(phenyl)-iodonium tetrafluoroborate with te/ra- -butylammonium benzenesulfinate in THF (i.e. homogeneous conditions) affords a moderate yield of l-phenylsulfonyl-3-phenylcy-clopentene and a low yield of the corresponding alkynyl sulfone (equation 51)32. With appropriately constructed alkynyliodonium ions, annulated cyclopentenyl sulfones are obtained (equations 52 and 53)32. 

TABLE 5. Cyclopentenyl sulfones and sulfonyl lactams from (ketoethynyl)iodonium and (amido ethynyl)iodonium triflates 17 and 18 with sodium / -toluenesulfinate in dichloromethane"... 

The propensity of the thiocyanate ion for alkynylation with alkynyliodonium ions has also been demonstrated with a series of bis(phenyliodonium)diyne triflates (equations 61 and 62)43. The efficient production of diynediyl dithiocyanates in these reactions may be contrasted with the favored formation of mono- and bis-cyclopentenyl sulfones from bisiodonium diyne salts and sodium/ -toluenesulfinate (see equation 57)86. 

Similar selectivities are obtained with substituted cyclopentenyl sulfones (prostaglandin precursors). and certain other acyclic a-sulfonyl carbanions48-50. 

Interaction of alkynyliodonium compounds with arylsulfinate salts is particularly interesting. When the R group of the alkynyl moiety lacks a y-CH bond, alkynyl sulfones (89, 90) are formed in excellent isolated yields [70, 71] [Eqs. (45), (46)]. When y-CH bonds are available, the intermediate unsaturated carbene (Scheme 3-3) prefers insertion over rearrangement and hence cyclopentenyl sulfones, 91, predominate, although some alkynyl sulfone formation is also observed as illustrated in [Eq. (47)] [72]. 

The kinetics of the reversible potassium r r/.-butoxide-catalyzed isomerization of cyclopentenyl- and cyclohexenyl-Az-butylsulfones in tert,-hwiy alcohol at 35°C showed that there is little resonance interaction between an a-ethyl-enic group and a sulfone function. ... 

B.P. Pyro Type K B.P. Pyro . See Sodium acid pyrophosphate BPS 319. See Phosphonic acid BPS 1. See4,4 -Dihydroxydiphenyl sulfone BR 662. See Phenolic resin BR. See Polybutadiene Brahmanol 3/071120, Brahmanol F 3/071130. See Butanol, 2-methyl-4-(2,2,3-trimethyl-3-cyclopentenyl)-Brain extract... 

Numerous organometal additions onto ene-sulfones are reported. A sulfonyl group secures powerful activation, and moreover, it can be readily removed by reduction or elimination. This makes the sulfonyl function a cherished auxiliary in natural product synthesis. A rational entry to d-(+)-carbacyclin (in 4.7% overall yield by a triply convergent synthesis) exemplifies the approach. The addition of the silyl-protected trans-(5)-3-hydroxy-l-octenyllithium onto cyclopentenyl phenyl sulfone 162 triggers a condensation with the allyl chloride tail. The carbacyclin skeleton constructed, the sequence is terminated by protodesilylation (using tetrabutylammonium fluoride hydrate), reductive removal (with lithium) of benzyl and benzenesulfinyl, and selective oxidation of the primary alcohol site (Scheme 1-117). ... 

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