2-Butenyl bromide

Reaction of p-keto esters (55a) and (55b) with 3-butenyl bromide gave the alkenes (55a) and (56b) in 63% and 57% yields. Oxidation of the terminal double bonds gave the 1,5-diketones (57a) and (57b) in... 

Preparation by reaction of 3-butenyl bromide with 5-allyl-2,4-dihydroxyace-tophenone in the presence of potassium carbonate and potassium iodide at reflux (26%) [2678,2679],... 

The reduction of 114 with LAH, followed by reaction with triphosgene, led to benzo[l, 2,5]thiadiazepin-6(4//)-one 1,1-dioxide 115, which upon treatment with Lawesson s reagent gave the corresponding thiocarbonyl derivative 116 (Scheme 26). The 1,2,5-thiadiazepine 115 was acylated by treatment with di-/-butyldicarbonate in the presence of AyV-dimethylaminopyridinc to afford 117, which is alkylated with 3-methyl-2-butenyl bromide or ethyl iodide to give 118 and 119, respectively <2002JHC81>. 

California Red Scale is a worldwide citrus pest which can be controlled by means of the pheromone 60. Cohen used reductive lithiation to generate versatile allylic nucleophiles applicable to this type of target.6 The allyl sulfide 61 is lithiated by BuLi and reacts with butenyl bromide a to sulfur to yield 63. Reductive lithiation (Li, DBB) of the product yields allyllithium 64. A regioselective reaction of this nucleophile with formaldehyde at the more substituted terminus is ensured by transmetallation to the allyl titanium 65, which gives 66 after treatment with formaldehyde and bromination. 

Configuration examination073 by H-nmr of the quaternary precursor of pentazocine (213a and b) and related compounds demonstrate that during quaternary salt formation, axial attack of the electrophile (from 3-methyl-2-butenyl bromide) occurs to yield predominantly 213b. This was consistent with earlier observations/174 175 An extensive study of the metazocines (base, HC1 salt, and methiodide) has been published,076 some results of which were later revised.077 178 ... 

This new alkylation procedure has been used for a simple synthesis of plastoquinune-1 (4) in 61 /o yield from 2,3-dimethylbenzoquinone and 3-methyl-2-butenyl bromide. Co-... 

When this cation reacts with Br, about 80% goes to one end and 20% to the other, giving a mixture of butenyl bromides. Notice that we have chosen one localized structure for our mechanisms. The choice is meaningless since the other structure would have done as well. It s just rather too difficult to draw mechanisms on the delocalized structure. 

Recently there has been interest in the synthesis of analogs of the naturally occurring mono- and diphosphate group. Corey and Volante ° have reported the alkylation of (dimethylphosphoryl)methyl-lithium with, for example, geranyl, famesyl and 3-methyl-2-butenyl bromides. Tlie products were assessed for their ability to inhibit the biosynthesis of squalene. McClard and coworkers described the alkylation of the phosphonylphosphinyl anion (14) to yield the P—C— P—C compounds, proven enzyme inhibitors (Scheme 13). The free acid derivatives were obtained by treatment of the alkylated products with bromotrimethylsilane. 

The diastereoselective production of homoallylic indium alkoxides can be accomplished by a kinetic resolution process [194]. The indium-mediated reaction of benzaldehyde with 2-butenyl bromide has always been observed to be unselec-tive. The use of alkoxide or halide modifiers in the reactions of allylindium reagents has previously been shown to provide synthetically useful reagents [195], Upon addition of 2-butenylindium sesquibromide to benzaldehyde it was determined that newly formed syn and anti homoallylic alcohols undergo decomposition at a similar rate, but as the concentration of the anti homoallylic alcohol reaches zero, the rate of decomposition of the syn alcohol slows dramatically. Thus, the syn homoallylic alcohol can be obtained in high diastereoselectivity, albeit low yield. 

The nucleophilicity of sulfur and its ability to stabilize a-carbanions provide sulfur compounds with unique opportunities for sigmatropic processes consecutive rearrangements are no exception. The formation of salt (140) via Sn2 alkylation of ( )-2-butenyl bromide (139) followed by deprotonation leads to the intermediate allyl vinyl ether (141) which, under the conditions of the deprotonation, undergoes a thio-Claisen rearrangement to afford thioamide (143 Scheme 10). Thermolysis of (143) at elevated temperature affords the Cope product (142) in addition to some of its deconjugated isomer. Several unique characteristics of the thio-Claisen sequence should be noted first, the heteroatom-allyl bond is made in the alkylation step, this connection teing not notrtudly practised in the parent Claisen reaction ... 

The T -butenyl bromide 259 was made by hydroalumination and bromination of but-l-yne 266. Hydroalumination occurs stereospecifically as (chapter 16) 267 and electrophilic replacement of aluminium by bromine occurs with retention at the sp2 centre.42... 

Reaction of 2-methyl-2-butenyl bromide with lithiumtetramethylpiperidide in the presence of olefins furnishes (2-methyl-1-propenyl)cyclopropanes with moderate cis selectivity17. 

The substituent X moves two atoms along the chain, and the double bond moves in the opposite direction to the position where X is still an allylic group. This migration can occur so readily that it is reasonable to regard the isomerization of allyl halides as true tautomerism. For example, equilibrium between 2-butenyl bromide and 1-methylallyl bromide is set up in a few hours at 75° 14... 

Also obtained by reaction of 3-methyl-2-butenyl bromide with pbloroacetopbenone in the presence of aqueous potassium hydroxide at r.t. for 24 h (29%) [4322],... 

Umani-Ronchi adapted the Furstner protocol to achieve the first catalytic, enantioselective variant of this reaction. The chiral chromium salen complex was prepared from the in situ reduction of the anhydrous CrCb to CrCl2 with an excess of manganese metal, followed by complexation with the salen ligand 8 in the presence of catalytic triethylamine." Then the addition of allylic chloride (9) to aldehydes 10 to give the allylic alcohols 11 in moderate yields and in up to 95% ee. The same groups employed the same conditions for the addition of 2-butenyl bromides to aldehydes to achieve up to 83 17 syn/anti of allylic alcohol products and for the addition of 1,3-dichloropropene to aromatic aldehydes to obtain the syn chlorohydrin adduct in modest yield which were further converted to optically active vinyl epoxides. The [Cr(salen)]-catalyzed addition of propargyl halides to aromatic aldehydes allowed the synthesis of enantiomerically enriched homopropargyl alcohols in moderate yields with up to 56% ee. ... 

The cyclopentane dione (0.154 g 5.58 x 10" mol) in dry ether (5 ml) is added to a vigorously stirred solution of sodium (0.3 g 1.3 x 10 mol) in dry ethanol (10 ml). After cooling to 0°C a solution of 3-methyl-2-butenyl bromide (0.075 g 5.03 x 10 mol) in ether (5 ml) is added. The mixture is stirred for 18 h, diluted with water, acidified (HCI) and extracted with ether. The ethereal layer is separated, washed with water, dried and concentrated in vacuo to an oil. Distillation yields 2-(3-methylbutanoyl)-5-(3-methyl-2-butenyl)-3,4-dihydroxy-4-(4-methyl-3-penten-1-ynyl)-2-cyclopentenone (0.084 g 44%) as a light-yellow oil with a boiling point of 100°C (bath temperature) at 5 X 10" mm Hg. 

Hulupone is synthesized in 54% yield by alkenylation of the sodium salt of dihydrohumulinic acid (see 8.4.3.1.1.) with 3-methyl-2-butenyl bromide (10). Cohulupone and adhulupone can be prepared similarly (9). However, cohulupone is more easily available from the natural colupulone. A series of analogous compounds has been obtained by reaction of dehydrohumulinic acid with various alkylating reagents (9,10). 

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