Allyl bromide allylation with

Otera et al. extended the tin-mediated allylation to 2-substituted allyl bromides.80 When 2-bromo and 2-acetoxy-3-bromo-l-propene were used, the allylation with tin produced the corresponding functionalized coupling products (Eqs. 8.36 and 8.37). In the case of 2,3-dibromopropene, the reaction occurred exclusively through allylation in the presence of the vinyl bromo group. The presence of other electrophiles such as a nitrile (-CN) or an ester (-COOR) did not interfere with the reaction. 

A new method has been developed for the synthesis of ( )-3-methyl Baylis-Hillman-type adducts with high E/Z (>93%) selectivity in modest to good yields. The process consists of two steps an indium-mediated allylation reaction and a simple base-catalyzed isomerization step (Eq. 8.61). Various aldehydes were allylated with allyl bromides using indium under very mild conditions in aqueous media and thus converted to the Baylis-Hillman-type adducts.150... 

Hg. Allylmercury bromide and diallylmercury are both stable in water. They can allylate aldehydes in aqueous media but, in the case of allylmercury bromide, activation with tetrahexylammonium bromide was necessary.186 The allylation reaction is chemoselective towards aldehyde on the contrary, ketone compounds are unaffected. 

The ylide obtained from (methyl)triphenylphosphonium bromide reacts with morpholine derivatives 597 to give phosphonium salts 598 which upon treatment with -butyllithium are converted to new ylides 599. In a reaction with aldehydes, ylides 599 form iV-(l,3-disubstituted allyl)-morpholines 602 (Scheme 94) <1996AQ138>. Another less common nucleophile that can be used for substitution of the benzotriazolyl moiety in Af-(a-aminoalkyl)benzotriazoles is an adduct of iV-benzylthiazolium salt to an aldehyde which reacts with compounds 597 to produce adducts 600. Under the reaction conditions, refluxing in acetonitrile, salts 600 decompose to liberate aminoketones 601 <1996H(42)273>. 

Allylic bromides reacted with KSCN/Si02 and BnNH30Ac/Al203 in one-pot gives the corresponding thioureas. Reactions of crotyl bromide with a series of alkylammonium acetates, with the exception of tert-butylammonium acetate, results in the corresponding thioureas (Scheme 49).130... 

Allylic bromination of 235 with excess CuBr and PhCCb-f-Bu (1 1 molar ratio) gives the separable allylic bromides 236 and 237 with 62% and 15% yield, respectively. Further treating the allylic bromide 236 with CuBr in CH3CN at 50° C leads to a mixture of 236 and 237, from which 25% of 236 and 69% of 237 can be separated. 

Surprisingly, only a single application of a copper(I)-catalyzed cross-coupling of metallated allenyl species has been reported [44]. The CuBr-catalyzed coupling of allenylmagnesium bromide (82) with allyl phosphate 83 provided 6-butyldeca-l,2,5-triene (84) in high yield, as depicted in Eq. 14.8. 

Hydroxycoumarins are alkylated under extremely mild basic liquiddiquid phase-transfer catalytic conditions to produce the ethers and 4-alkylated derivatives 141 ]. The major product tends to be the ether (50-60%) but the yield of the C-alkyl-ated product is significant with allyl bromide and with propargyl bromide, where rearrangement of the allenic derivative occurs. 

An additional report describes Te/Zn exchange of diaryl tellurides and diaryl ditelluride by treatment with Zn under Ni catalysis." The resulting Zn derivatives submitted to trans-metallation with CuCN-2LiCl and subsequent allylation with aUyhc bromide, furnishes the expected product in high yield. 

The alkyl substituent meta to the methoxy substituent was easily introduced into the symmetrical diamide 72 by yet another ortholithiation. Allyl electrophiles react poorly with aryllithiums, so the ortholithiated amide 73 was first transmetallated to the Grignard reagent before allylation with allyl bromide to give 74. 

The optically pure (-)-(3/ ,4S )-cA-4-methyl-3-ethenylbutyrolactone 31 ([ ]u —53.0, CHC13) is available from D-glucose23. Its allylation with allyl bromide under the usual conditions (LDA, THF, —78 °C) gave the trisubstituted lactone 32 ([ ]D —27.8, CHC13) in a highly diastereoselec-tive reaction. 

Scheme 6 Simple orbital correlation diagram depicting the interaction of a bromide ion with an allyl radical. The reverse process represents the intramolecular concerted ET.

Allyl bromide reacts with nickel carbonyl in benzene to give the volatile ir-allyl complex [NiBr(ir-C3H6)]2 as a violet-red solid (75). 

Hydrogen bromide reacts with NBS to produce a Br2 molecule, which reacts with the allylic radical to form 3-bromocyclohexene, and a bromine radical is produced to continue the chain. 

Allyl iodide and bromide react with la to yield the dihalides [l]15b and [2]15a, respectively, in about 15% yield. The usual adducts were not observed113 (equation 15). 

The hydrobromination of a number of halogenated alkenes has been examined. Allyl bromide reacts with HBr in the absence of peroxides, or upon addition of antioxidants121 or FeCb,61 or in acetic acid,122 to produce primarily 1,2-dibromopropane (equation 74). Allyl chloride behaves similarly.123... 

Kotarska et a/.106-282 attributed the 3-substituted structures to the products obtained from the pyrido[l,2-a]pyrimidine (63 R = H) by alkylation with either 1-chloromethylnaphthalene or allyl bromide, or with benzyl chloride in ethanolic potassium hydroxide in the presence of potassium iodide. The melting point of the 3-benzyl compound agreed with the earlier literature datum but that of the 3-allyl compound differed by more than 20 C.100,112... 

Additions to functionalized three-carbon olefins have been studied extensively. We have used methyl acrylate as a standard olefin since it always reacts only at the terminal carbon and the a,/3-double bond in the product is always trans. The stereospecificity of its reactions with vinylic halides varies with structure. The simple 1-halo-l-alkenes with methyl acrylate under normal conditions give mixtures of E,Z- and E,E-dienoates. The reaction is more selective with the bromides than with the iodides and the stereoselectivity increases with increasing triphenylphosphine concentration. This occurs because the excess phosphine displaces the hydridopalladium halide group from the diene 7r-complex before readdition to form the ir-allylic species occurs (see Equation 6). The disubstituted vinylic bromides react stereospecifically with methyl acrylate (4). 

Allylation of organic halides. T wo laboratories2 have reported briefly that in the presence of a radical initiator organic halides undergo allylic substitution reactions with allyltrialkyltin compounds in moderate yield. This reaction was used in a recent Synthesis of the neurotoxin (+ )-perhydrohistrionicotoxin (7) to introduce the n-butyl tide chain.3 AI BN-catalyzed reaction of the bromide 2 with 1 proceeds in unexpectedly igh yield and with complete stereocontrol to give a single product 3. It is the tndesired isomer, but the desired stereochemistry is obtained by epimerization of the Intermediate ketone 5. The hydroxy lactam (6) had previously been used for the Synthesis of 7. 

Homoallylic alcohols. Tn the presence of metallic tin, both allyl iodide and bromide react with carbonyl compounds at room temperature to form homoallylic alcohols in 75 90% yield. Presumably a diallyltin dihalide is formed initially.1 Examples ... 

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