Chloride with Wittig reagents

The di-, tri-, and tetra-methyl-3-thietanones have been prepared by the ring-closure of cr,a -dibromo-ketones with sulphide ion. The stereochemistry of the dimethyl compounds was determined by reduction to the thietanols. 3-Thietanones can also be prepared by the reaction of ketones with thionyl chloride. The Wittig reagent (85) has been prepared. ... 

The acylation of Wittig reagents provides the most convenient means for the preparation of allenes substituted with various electron-withdrawing substituents. The preparation of o-allenic esters has been accomplished by the reaction of resonance-stabilized phosphoranes with isolable ketenes and ketene itself and with acid chlorides in the presence of a second equivalent of the phosphorane. The disadvantages of the first method are the necessity of preparing the ketene and the fact that the highly reactive mono-substituted ketenes evidently cannot be used. The second method fails when the a-carbon... 

Olefination of the Aldehyde 178 using a stabilized Wittig reagent followed by protecting group chemistry at the lower branch and reduction of the a,p-unsaturated ester afforded the allylic alcohol 179 (Scheme 29). The allylic alcohol 179 was then converted into an allylic chloride and the hydroxyl function at the lower branch was deprotected and subsequently oxidized to provide the corresponding aldehyde 161 [42]. The aldehyde 161 was treated with trimethylsilyl cyanide to afford the cyanohydrin that was transformed into the cyano acetal 180. The decisive intramolecular alkylation was realized by treatment of the cyano acetal 180 with sodium bis(trimethylsi-lyl)amide. Subsequent treatment of the alkylated cyano acetal 182 with acid (to 183) and base afforded the bicyclo[9.3.0]tetradecane 184. 

Selective reactions. Wittig reactions of 1 with an aldehyde are possible in the presence of keto, ester, and amino groups.2 Wittig reagents react under normal conditions with acid chlorides. The stabilized ylid I reacts preferentially with the acid chloride group of 4-lormylhcnzoyl chloride (2) lo give 3 as the major product. ... 

Heptaphylline (1) has been synthesised by sequential C(3)-formylation and C(l)-isopentenylation of 2-hydroxycarbazole. l-Formyl-2-hydroxy-3-methyl-carbazole reacts with the Wittig reagent from 2-methylprop-l-en-3-yltriphenyl-phosphonium chloride-sodium hydroxide to generate girinimbine (2a) 2-hydroxy-3-methylcarbazole reacts with citral to give ( )-mahanimbine (3a). 

A second publication records a few other examples (198). As mentioned previously, Frisch and Lyons attempted a condensation of phosphorus pentachloride with an aryl Grignard reagent but obtained only the tertiary phosphine and the impure phosphinous chloride (55). It will be recalled that the Wittig reagent is prepared by treatment of an alkyltri-phenylphosphonium halide with phenyllithium (182). 

Vinyl sulfides can also function as acyl anion equivalents but their preparation has not as yet been discussed. In one common synthesis, a Wittig reagent (362, sec. 8.8.A) reacted with benzenesulfenyl chloride to produce a new ylid (363), which condensed with benzaldehyde to give a 79% yield of the vinyl sulfide, 364 361,364 When 364 was treated with mercuric salts, a 73% yield of phenylacetone was obtained. In the second approach, a vinyl tin compound (365)362 treated with methyllithium, and lithium-metal exchange provided 366.Alkylation with iodomethane gave a 91% yield of 367 and treatment with titanium tetrachloride led to a 75% yield of l,l-diphenylacetone.2 i... 

A new procedure for the elaboration of benzylisoquinolines has been developed. Treatment of 6,7-dimethoxy-l-chloroisoquinoline with the Wittig reagent (16) prepared from veratryl chloride and tri-n-butylphosphine furnished, after workup, a 74% yield of papaverine. 

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