1- Bromo-2,5-hexadiene

Bromo-2,5-hexadiene, 41, 51 3-Bromo-l,5-hexadiene, 41, 51 Bromohexadicne (mixture), 41, 50... 

Hexadiene, 55, 109 Hexanoic acid, 55, 27 Hexanoie acid, 2-bromo-, 55,30... 

Some reactions via intermediate alkylideneallyl cations have been reported. Solvolysis of 3-bromo-2,5-dimethyl-2,4-hexadiene in ethanol at 100 °C for 80 min gives 5-ethoxy-2,5-dimethyl-2,3-hexadiene in quantitative yield (Scheme 2) (5). This indicates that ethanol selectively attacks the sp2 carbon of the intermediate alkylideneallyl cation. A similar selectivity has been observed in the solvolysis of 2,3-dienyl alcohols (6), and is in agreement with the charge distribution. A cycloaddition reaction via an alkylideneallyl cation intermediate has been reported as illustrated in Scheme 3(7). 

Scheme 6.39 Generation ofl62 by -elimination from 1 -bromo-1,4-cyclo-hexadiene (174), trapping of162 by furan and 2,5-dimethyl-furan and deprotonation of162 by KOtBu.

The addition of HBr to 2-methyl-l,3-pentadiene, 1-bromo-1,3-butadiene, 1-phenyl-1,3-butadiene and 2,4-hexadiene produces 2,4-dibromo-2-methylpentane, 1,3-dibromo-l-butene, 3-bromo-l-phenyl-1-... 

Hegedus and Varaprath studied the reactions of various bromodienes with Ni(CO)4 and with bis(cyclooctadiene)nickel. l-Bromo-2,5-hexadiene and 2-bromomethyl-1,3-butadiene give the stable products 62 and 63, respectively, which resemble allyl nickel halides in their properties (217). Similar compounds had been prepared several years previously from geranyl halides (218). l-Bromo-2,4-pentadiene and l-bromo-2,4-hexadiene, however, formed intractable materials which could not be isolated and purified. In these cases the red color of the solution which was first produced faded and NiBr2 was deposited. The desired compounds, however, could be generated in situ at — 30° C and used in coupling reactions with aryl, alkenyl, and allyl halides (217). 

Mo(CH3CN)3(CO)3 reacts with allyl chloride to form MoCl( /3-C3H5)-(CH3CN)2(CO)2 (214). 1-Bromo- and l-chloro-2,4-hexadienes give analogous f 3-pentadienyl complexes (219). 

Propargyl bromide 1-Propyne, 3-bromo- (8,9) (106-96-7) Dimethyl acetylenedicarboxylate Acetylenedicarboxylic acid, dimethyl ester (8) 2-Butynedioic acid, dimethyl ester (9) (762-42-5) l,2-Hexadien-5-yne (8,9) (33142-15-3)... 

In a refinement of the previous synthesis 59) compound 159 was alkylated with 6-bromo-l,2-hexadiene in the presence of sodium hydride in DMF giving 172 containing all the carbon atoms necessary for completion of the carbon skeleton. Irradiation in the manner previously described gave 173 in 70% yield and this compound was converted into the lactam 174 in a series of reactions similar to those used in the previous synthesis to convert 161 into 168. Lactam 174 was then converted into racemic 12-epilycopodine by established routes. 

Hydrogen halide is also removed when an unsaturated halide is distilled from its mixture with a solid alkali hydroxide 4-methyl-1,3-hexadiene, for example, was prepared in this way from 4-bromo-4-methyl-l-hexene.109... 

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