3-Phenylallyl bromide

Another type of cationic initiation procedure starting from an unsaturated compound has been proposed 49). 3-Phenylallyl bromide is reacted in THF solution with AgSbF6 whereby a poly-THF macromonomer bearing a styryl residue at the chain end is formed ... 

There is one more way for conversion of ort/to-nitroarylacetonitriles into indoles. Alkylation of such nitriles with allyl or benzyl halides followed by treatment of the compounds obtained with basic agents results in a multistep transformation, which is likely to proceed via intermediate nitrosoarenes, to produce 1-hydroxyindoles. For instance, alkylation of ort/io-nitroarylacetonitriles with 3-phenylallyl bromide gives the compounds that in the presence of chlorotri-methylsilane and triethylamine undergo cyclization into 3-cyano-l-hydroxy-2-vinylindoles (Scheme 70) [188]. Presumably, this reaction proceeds via 0-silylation of the nitronate anion and 1,5-elimination of trimethylsilanol from the intermediate trimethylsilyl nitronate, followed by cyclization and a hydrogen shift. 

The best results were obtained with 20 mol% camphor-derived sulfonium salt 230, with 1.5 equivalents of 3-phenylallyl bromide and one equivalent of chalcone at 0°C in a mixture of fert-butyl alcohol and acetonitrile (2.5 1). The cyclopropanation product was obtained in moderate diastereoselectivity (86/14), good enantiose-lectivity (82% ee) and in high yield (92%). The method could be extended to a variety of a,P-unsaturated carbonyl compounds (Table 7.16). The chiral sulfide 228 could also be employed directly without preformation of the sulfonium salt 230 with similar results. 

Allyl chloride and j3-phenylallyl bromide have been converted into ailyl azide and )3-phenyIallyl azide, but to differentiate between possible mechanisms involved in these reactions labelling studies would be necessary. The primary and secondary allylic chlorides, geranyl chloride and a-butylallyl chloride appear to undergo normal... 

Synthesis of 2-Phenylallyl-ended Poly(a-methylstyrene). Synthesis of poly(a-methylstyrene) having an end double bond was described in our previous papers(15,16). Briefly, to the reactor (100 mL flask equipped with three-way stopcock), THF (6.6 mL), sec-butyllithium (0.34 mL 0.26 mmol) and a-methylstyrene (1.18 g 10 mmol) were added in this order via a syringe at -78 C. The color of the mixture turned brownish red immediately. The reaction was allowed to continue for 20 min. For an end-modification reaction, a 2-5 times excess molar amount of the end coupling agent, 2-phenylallyl bromide, was added to the living polymer solution and allowed to react for 20 min. The resulting mixture was analyzed by GPC and then poured into a large excess of methanol. The precipitate was purified by three successive reprecipitations from THF solution into methanol. The obtained polymer was freeze-dried with benzene to remove the solvents employed. Yield of the polymer was ca. 95%. 

In the presence of bromide, the oxidation of alkenes by Mn(OAc)3 in acetic acid readily occurs it 70-80 °C and produces allylic acetates in good yields. Thus cyclohexene is oxidized to cyclo-lexenyl acetate in 83% yield,508 and a-methylstyrene to j3-phenylallyl acetate in 70% yield,509 vith a mechanism involving allylic hydrogen abstraction by bromine atoms coming from the ixidation of bromide by MniU (equation 206). 

Most of the work concerned with micellar catalysis of nucleophilic substitution refers to reactions of the Aac2 and SN2 types and will not be reviewed here. To date only a few systems have been examined in which a micellar medium affects the partitioning of solvolytic reactions between unimolecular and bimolecular mechanisms. The effects of cationic (hexadecyltrimethylammonium bromide = CTAB) and anionic (sodium lauryl sulfate = NaLS) micelles on competitive SN1 and SN2 reactions of a-phenylallyl butanoate 193) have been investigated189. The rate of formation of the phenylallyl cation 194) is retarded by both surfactants probably as a consequence of the decreased polarity of the micellar pseudo phase. The bimolec-... 

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