Sulphoxides allenic

Reaction of alkynols 156 with benzenesulphenyl chloride afforded either the vinylacety-lene sulphoxides 157 or the allene sulphoxides 158 depending upon the substitution pattern of alkynols 156. Vinylacetylene sulphoxides 157 result from a [2,3]-allylic rearrangement of the sulphenate ester 159 (equation 88). In the case of the cyclic... 

TABLE 14. Allenic sulphoxides from propargylic alcohols and sulphenyl chlorides, RSC1... 

A closely related reaction of (—)-(S)-276 with the Grignard reagents obtained from a-acetylenic halides leads to the formation of mixtures of acetylenic sulphoxides 290 and allenic sulphoxides 291363 (equation 161). The latter compounds are most probably formed via transition state 292, which is analogous to 289. On the other hand, hex-l-ynyl p-tolyl sulphoxide 293 is smoothly prepared from hex-1 -ynylmagnesium bromide and (— )-(S)-276363 (equation 162). 

Rearrangement of acetylenic sulphenates to the allenic sulphoxides 151 was discovered when the synthesis of propargylic ester of trichloromethanesulphenic acid 152 was attempted (equation 86). This reaction is of general scope and gives very good yields of allenic sulphoxides (Table 14) from structurally diverse cohols and various sulphenyl chlorides Reaction of alkynols 153 with benzenesulphenyl chloride in the presence... 

Michael additions of malonate to allenic sulphoxides (408) proceed efficiently to give homologues (409) which, after [2.3]-sigmatropic... 

The 5>>n-elimination of sulphenic and selenenic acids from unsaturated sulphoxides and selenoxides introduces a further site of unsaturation, examples being the addition of allyl alcohols to allenic sulphoxides to give ff-(allyloxy)vinyl sulphoxides... 

Heating compounds containing the system C C—C—S—C=C in hexa-methylphosphoramide (HMPA) gives 2if-thiopyrans (247). Isomeric thio-phens appear when the reaction is conducted in the presence of amines. Allene sulphoxides (248) are readily available by reaction of alkynols with sulphenyl chlorides to form labile sulphenyl esters, which rearrange to (248). The two chiral centres in these molecules (sulphoxide and allene) result in... 

Allenic sulphoxides undergo rapid and stereospecific desulphurization to give allenes with retention of configuration on treatment with four molar equivalents of methyl-lithium in THF at —70 C. ... 

A rapid approach to a-sulphinyl-ketones is the Lewis-acid-catalysed sulphinyl-ation of trimethylsilyl enol ethers by sulphinyl chlorides. In the absence of the Lewis acid stannic chloride, yields of the sulphoxide were very low. Allenic sulphoxides are readily converted into the P-keto-sulphoxide via the intermediate enamine [equation (38)]. Allene sulphones also add allylic alcohols under basic... 

Allenic sulphoxides ArSOCH=C==CR R are available through the reaction of sulphenyl halides with propargyl alcohols HC CCR R OH. Friedel-Crafts reactions with toluene>p-sulphinyl chloride in the presence of AICI3, SnCh, or SbCl, give aryl p-tolyl sulphoxides, and an analogous product is obtained unexpectedly, using toluene-p-sulphonyl chloride with isoquinoline as substrate in the presence of excess NaH. ... 

The 2-vinylpyrrolidines 321 are formed in up to 99% diastereomeric excess by the ring closure of the allenic sulphides or sulphoxides 320 (R = PhS or PhSO), induced by silver(I) ions376. 

Alkylation of the sulphone (111) with Bu"Li-Me3SiCH2l gave the /8-silyl-sulphone (112) which with Bu NF gave ° 3-methylene-5a-cholestane (113). Alkenyl sulphoxides, such as (114), were reduced to the alkenyl sulphides, without double-bond isomerization, using EtNlgBr-Cul " and the terminal allene (115) was prepared by treatment of (114) with LTMP. Reaction of... 

Further investigations of oxidations by dimethyl sulphoxide activated by oxalyl chloride have shown the system to be of general use, although allenic and acetylenic alcohols are not oxidized. The same reagent activated by dicyclo-hexylcarbodi-imide has been reported to yield ketones from alcohols in the presence of dithianes/°... 

J. Berlan and K. Koosha, J. Organometallic Chem., 1978,152,359 ibid., 153,99,109. Me2CuLi and allenic phosphine oxides, carbonyls, sulphones, sulphoxides. 

The transformation of non-aromatic ketones into their corresponding terminal allenes has proven to be a difficult process. Posner has now shown that the sulphoxides (88), derived from condensation of a ketone with lithium diethyl-phenylsulphinylmethylphosphinate, undergo regiospecific a-alkylation the terminal allenes are then readily formed by base-catalysed elimination from the alkylated product (89), with no formation of the corresponding acetylenes (Scheme 33). Chan also describes conditions whereby aldehydes and ketones can be condensed with vinyl carbanions a- to silicon, to give terminal allenes or allyl chlorides. 

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