2-Propenylmagnesium bromide

Stock solutions of 2-propenylmagnesium bromide (1-2 M) in diethyl ether and 2-propenyl-magnesium chloride in THF are commercially available. 

The reactions of a-methyl-branched acylsilanes with 2-propenylmagnesium bromide exhibit surprisingly high diastereoselectivilies, although further improvement is accomplished by application of allyltrimethylsilane/ titanium(IV) chloride (> 100 I)27. The fluoride-induced desilylation proceeds with retention of configuration. 

The direct allylation of 2-phenylpropanal proceeds with much lower selectivity [2-propenylmagnesium bromide 73 27 allyltrimethylsilane/titanium(IV) chloride 67 33]27. 

The titanium complex 4, prepared from (A./ )-2,3-0-isopropylidenc-1,1.4,4-tetraphenyl-1,2,3,4-butanetetrol7,113 and chlorotriisopropoxytitanium or tetraisopropoxytitanium, is treated with 2-propenylmagnesium bromide. The resulting titanate affords, with benzaldehyde, ( —)-(5)-l-phenyl-3-butenol. Several further attempts, which do not include allylation, have also been reported113, as have examples using the dichloride114. 

Exercise 31-10 The nmr spectrum of 2-propenylmagnesium bromide in ether is shown in Figure 31-4. With the aid of the discussion in Sections 9-10C and 9-10E and the knowledge that the CH2 resonance of ethylmagnesium bromide comes at 38 Hz upfield from tetramethylsilane, sketch the nmr spectrum you would expect for CH2=CHCH2MgBr. Consider possible ways of reconciling your expected spectrum with the actual spectrum shown in Figure 31-4. (Review Section 27-2.)... 

Figure 31-4 Nmr spectrum of 2-propenylmagnesium bromide in diethyl ether solution at 60 MHz with reference to tetramethylsilane at 0 Hz. The off-scale bands are due to the diethyl ether, and the signals designated C6H10 are due to 1,5-hexadiene (coupling product resulting during formation of the Grignard reagent).

Use of 3,3-dimethylcyclopropene to make cis-isochrysanthemic acid (294) with 2-methyl-2-propenylmagnesium bromide followed by carbonatation was mentioned in Vol. 4 (p. 487, Ref. 244) a new preparation of the cyclopropene and its reaction with prenylmagnesium bromide (15, R = MgBr) have now been described. ... 

Chelation-controlled addition of 2-propenylmagnesium bromide to 589 affords a 4 1 mixture of allylic alcohols 601 and 285. Since the stereochemistry of the major syn isomer 601 does not possess the correct configuration for the C-5 carbon of the fragment, it is converted to the desired anti isomer 285 by oxidation to an intermediate enone followed by reduction of the carbonyl with zinc borohydride (20 1 ds). 

Quinoline and isoquinoline react with organometallic reagents exactly as pyridine does (Section 25-6). Give the products of their reaction with 2-propenylmagnesium bromide (allylmag-nesium bromide). 

A 0.5-M solution of 2-propenylmagnesium bromide in THF (100 mL, 50 mmol) is added drop by drop to a solution of l,l-dimethyl-2-oxa-l-sila-indan (prepared by lithiation of 0-bromophenol THP ether with butyllithium followed by p-toluenesulfonic catalyzed deprotection, 7.5 g, 46 mmol) in THF (50 mL) cooled with ice at 0 °C, and the resulting mixture is stirred at rt for 9 h. The mixture is diluted with diethyl ether and the ethereal solution was carefully washed sequentially with a saturated NH4CI aq., with water, and finally with brine, and then dried over anhydrous MgS04. After removal of the solvents in vacuo, the residue is distilled under vacuum to give the title compound in 89% yield as a colorless oil, bp 75 °C at 0.4 mmHg. ... 

The iron(m) intermediates in Scheme 3 serve as focal points for the formation of the side products. For example, metathetical exchange of propenyl-iron(lll) with Grignard reagent would afford propenylmagnesium bromide in Equation 30.(36)... 

Dimethyl 3-(2-methyl-l-propenyl)-2,2-dimethylcyclopropane-l,l-dicarboxylate (324) is synthesized by the reaction of (2-halo-2-methylpropylidene)malonate (291) with 2-methyl-l-propenylmagnesium bromide (323). The cyclopropane is accompanied by the malonoester (325) and a butanolide (326) formed by nucleophilic attack of an ester enolate (equation 101) . ... 

A few years later, by a different research group, the idea was proposed to trap, or observe, the intermediate radical or radical anion [47]. cis-Propenylmagnesium bromide, a vinylic Grignard reagent, reacted with benzophenone to yield exclusively the normal. 

Reduction of prochiral 1,3-diketone A with baker s yeast gives hydroxy ketone B of 99% ee.10 The ketone B was converted to unsaturated ketone C, which was treated with (Z)-l-propenylmagnesium bromide in the presence of cerium(III) chloride to give a mixture of D and E. This mixture was directly subjected to oxy-Cope rearrangement to give F from D. The exo-isomer E was recovered unchanged. 

In a second chelation-controlled addition, 286 is converted to 602 by the addition of trans-propenylmagnesium bromide to the acetyl carbonyl, followed by lactonization. Dioxanone—... 

Some dienes have one olefin endocychc to a ring. One such diene has been prepared by addition of propenylmagnesium bromide to a ketone, followed by dehydration [23]. In another case, such a diene was prepared by an intramolecular aldol condensation, followed by Wittig olefination [24]. 

Ethyl ethylidenemalonate dil. with an equal volume of anhydrous ether added dropwise with stirring to 1-propenylmagnesium bromide prepared from 1-pro-penyl bromide and Mg in tetrahydrofuran, and allowed to warm to room temp. ethyl (l-methylbut-2-enyl)malonate. Y 80%. F. e. s. T. Guvigny and... 

Synthesis of unsatd. ketones. A soln. of propenylmagnesium bromide in tetra-hydrofuran added slowly at —65° with vigorous stirring during 4 hrs. to 50% excess butyric anhydride in the same solvent, then allowed to warm to room temp. 2-hepten-4-one. Y 73%. F. e. and methods s. G. Martin, A. ch. [13] 4, 541 (1959). 

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