Allenic sulphoxides reactions

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... 

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... 

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 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. ... 

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... 

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