Bromopropenes

T rimethylsilylethoxy-mcthyl)-2-(tri-n-butyl-stannyl)indole 3-Bromopropene, Pd,(dba)j, tri-(2-furyl)phosphine 93 [1]... 

T rimethylsilylethoxy-methyl)-2Ttri-n-butyl-slannyl)indole 2-Bromopropene, PdfPPhjljClj 62 [2]... 

I I ndol-1 -ylmagnesium bromide 3-Bromopropene, benzene, 70 10-14hat20X [4]... 

Chemical shift nonequivalence can occur when two environments are stereochem ically different The two vinyl protons of 2 bromopropene have different chemical shifts... 

Cyclohexyl-2-bromopropene-i has been made by the action of cyclohexylmagnesium bromide on 2,3-dibromopropcne.i Hull. soc. (him. (4) 211, 328 (i[Pg.21]

Benzylamine adds smoothly to 3,3,3-tnfluoro-2-bromopropene. The bromo-aUcy lamine thus formed cyclizes to 1 -benzyl-2-trifluoromethy lazindine [ 108] (equation 94). 

It has been shown (87KGS787) that the dehydrobromination of (2-bromopropen-3-yl)pyrazole 23 by KOH in triethyleneglycol (150°C, 0.5 h) gives the intermediate allene which is transformed into 3,5-dimethyl-l-phenyl-4-prop-l-ynyl-l/7-pyrazole (24) (Scheme 33). 

Unlike the acid-catalyzed ether cleavage reaction discussed in the previous section, which is general to all ethers, the Claisen rearrangement is specific to allyl aryl ethers, Ar—O—CH2CH = CH2. Treatment of a phenoxide ion with 3-bromopropene (allyl bromide) results in a Williamson ether synthesis and formation of an allyl aryl ether. Heating the allyl aryl ether to 200 to 250 °C then effects Claisen rearrangement, leading to an o-allylphenol. The net result is alkylation of the phenol in an ortho position. 

Similarly 2,3-dibromo- and 2-acetoxy-3-bromopropene react with carbonyl compounds without the need for an inert atmosphere62. 

Similar reactions were also carried out with 3-bromopropene, l-bromo-2-butene, 3-bromocy-clohcxcnc. and 3-bromocyclooctene in refluxing ethanol as solvent24 . Zinc-mediated Barbier reactions can be accomplished with high yields in a mixture of saturated aqueous NH4C1/THF (5 1), at room temperature or below using a 1.2 to 2-fold excess of the halide over the carbonyl compound25. 

The chromium reagent, prepared from 3-bromopropene, exhibits a good ability to discriminate between axial and equatorial attack in 4-fcrf-butylcyclohexanone1. 

Change of base (pyridine, aniline, water) had no obvious effect on the steric course of the reaction (59). Rather surprisingly, it appears that the reactions of the cis and trans isomers of 1-bromopropene with the hydride [Co(CN)5H] give different products this eliminates an initial addition of Co—H to the double bond, since this would lead to the same product for the two isomers 105). Vinyl chloride apparently reacts only with [Co salen] , and not with the hydride, to form the CH2=CHCo complex 43) the same may be the case with the BAE complexes 40). 

Scheme 1.12 Base catalysed elimination from 2-bromopropene...

Entry 9 uses the oxaborazolidine catalysts discussed on p. 505 with 2-bromopropenal as the dienophile. The aldehyde adopts the exo position in each case, which is consistent with the proposed TS model. Entry 10 illustrates the use of a cationic oxaborazolidine catalyst. The chirality is derived from trans-1,2-diaminocyclohcxanc. Entry 12 shows the use of a TADDOL catalyst in the construction of the steroid skeleton. Entry 13 is an intramolecular D-A reaction catalyzed by a Cu-Ws-oxazoline. Entries 14 and 15 show the use of the oxazaborolidinone catalyst with more complex dienes. 

Bromomethane, see Methyl bromide Bromopentane, see Amyl bromide Bromopropane, see Propyl bromide 3-Bromopropene, see Allyl bromide 3-Bromopyne, see Propargyl bromide ... 

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