Ethers, allyl thiophenyl

One of die most popular reactions in organic chemistry is dissolving metal reductions [1-3], Two systems are frequently used - sodium dissolved in ammonia with alcohol and lithium dissolved in alkylamines [4]. Although calcium is seldom used, it has been successfully applied to the reduction of a variety of compounds and functional groups [5], including aromatic hydrocarbons, carbon-carbon double and triple bonds, benzyl ethers, allyl ethers, epoxides, esters, aliphatic nitriles, dithianes, als well as thiophenyl and sulfonyl groups. 

The only example of an N-sulfonyl ketimine participating in an ene reaction involves the tosyl imine of trifluoroacetone 266 [90] [Eq.(62)]. When heated with a terminal olefin such as allyl benzene (265) in refluxing xylene, imine 266 leads to ene product 267 in moderate yields. However, internal alkenes gave significantly lower yields of ene products. The inefficiency of the ene process with more highly substituted olefins was ascribed to unfavorable steric effects due to the bulky trifluoromethyl groups. Interestingly, with /J-methyl styrene and allyl thiophenyl ether, [2+2]-cycloadducts were detected rather than ene products. 

In addition to the well exploited radical additions to enamides, thiovinyl ethers have been shown to be suitable intramolecular acceptors for aryl radicals. By placing a thiophenyl substituent on terminal alkene of 33, the cyclization to 34 occurred exclusively in the 6-exo mode and was not complicated by internal hydrogen abstraction from the allylic positions of the alkene (Scheme 13) [83, 84]. 

Lewis acid, In(0CF3S02)3, catalysed allylic C—H oxidation of aryl cycloalkenes by l-(propyl thio)pyrrolidine-2,5-dione in the presence of CH2CI2 and various nucleophiles (ROH, RCO2H, RSO2NH2) resulted in the formation of allylic ethers, esters, and sulfonamides in 52-83% yields electron-rich substrates were the most reactive. Other aryl cycloalkenes such as 1-naphthyl, l-(3-thiophenyl)-cyclohexene, 1-phenylcycloheptene, and 1-phenylcyclopentene were suitable substrates. Mechanistic studies showed that the sulfenamide played an important role in converting the allyl sulfide intermediate into the products. ... 

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