Bromides cinnamyl

A halogenating system related to the preceding case is formed by the reaction of triphenylphosphine with molecular bromine or chlorine. The system is not as sensitive to moisture as the phosphine-carbon tetrahalide system (see preceding section), but it suffers from the disadvantage that hydrohalic acids are produced as the reaction proceeds. Nevertheless, sensitive compounds can be successfully halogenated by the system, as exemplified by the preparation of cinnamyl bromide from the alcohol. 

It is well known that aziridination with allylic ylides is difficult, due to the low reactivity of imines - relative to carbonyl compounds - towards ylide attack, although imines do react with highly reactive sulfur ylides such as Me2S+-CH2-. Dai and coworkers found aziridination with allylic ylides to be possible when the activated imines 22 were treated with allylic sulfonium salts 23 under phase-transfer conditions (Scheme 2.8) [15]. Although the stereoselectivities of the reaction were low, this was the first example of efficient preparation of vinylaziridines by an ylide route. Similar results were obtained with use of arsonium or telluronium salts [16]. The stereoselectivity of aziridination was improved by use of imines activated by a phosphinoyl group [17]. The same group also reported a catalytic sulfonium ylide-mediated aziridination to produce (2-phenylvinyl)aziridines, by treatment of arylsulfonylimines with cinnamyl bromide in the presence of solid K2C03 and catalytic dimethyl sulfide in MeCN [18]. Recently, the synthesis of 3-alkyl-2-vinyl-aziridines by extension of Dai s work was reported [19]. 

CijHkjO 104-54-1) see Chloramphenicol Zipeprol rrans-cinnamyl alcohol (C HiqO 4407-36-7) see Reboxetine cinnamyl bromide... 

Regioselectivity is independent of the geometry of the double bond and either E- or Z-cinnamyl bromide coupled with /-butanal to give the same regioisomer. 

Iminium ions, generated in aqueous solution from secondary amines and formaldehyde, undergo a Barbier-type allylation mediated by tin, aluminum, and zinc. The reaction is catalyzed by copper and produces tertiary homoallylamines in up to 85% yield.67 The imines generated in situ from 2-pyridinecarboxaldehyde/2-quinolinecarboxaldehyde and aryl amines undergo indium-mediated Barbier allylation in aqueous media to provide homoallylic amines.68 Crotyl and cinnamyl bromides... 

When this distillation was replaced by a procedure in which the acetonitrile was removed with a rotary evaporator and steam bath, and the product was extracted from the triphenylphosphine oxide with small portions of acetonitrile totaling ca. 250 ml., the checkers obtained an improved yield (79%) of cinnamyl bromide. 

Cinnamyl bromide has been prepared from cinnamyl alcohol by the action of hydrogen bromide in cold acetic acid2 and of phosphorus tribromide in boiling benzene.3 It has also been... 

Cinnamyl bromide, 48, 51 2,4,6-Collidine in hydrolysis of esters to acids, 45, 8... 

Cydopropylbenzene has been prepared by decomposition of 5-phenylpyrazoline,4 addition of hydrogen bromide to cinnamyl bromide followed by cyclization with zinc,6 decarboxylation of... 

Palladium nanoparticles coated with a fluorous-derivatized surfactant (or stabilizer) have been used to catalyse Heck and Suzuki reactions in a C8F17Br-benzene biphase [11], The reaction between phenylboronic acid and cinnamyl bromide was investigated and the reaction is illustrated in Scheme 10.10. 

The effect of the leaving group was briefly examined, but cinnamyl bromide gave a substantially lower ee (38%). Cinnamyl dimethyl phosphonate, or acetate, gave very poor results. The cyclohexyl-substituted allylic acetate 21, on the other hand, afforded a completely y-selective reaction, but the product turned out to be racemic. Changing the Grignard reagent halide from bromide to either chloride or iodide resulted in very low ees. 

Typical procedure Phenylcinnamyl telluride (prepared from sodium phenyl tellurolate, 1 mmol, and cinnamyl bromide, 1 mmol in EtOH, 10 mL) was treated with Phl=NTS (1.5 mmol) and the mixture was stirred at 25°C for 20 h. After removal of the solvent, the product was purified by column chromatography on Si02 (eluent hexane/AcOEt). 

With cinnamyl bromide affords flunarizine (23). Flunarizine is also a coronary vasodilator. 

Later, a similar coupling reaction between allyl bromide or cinnamyl bromide with Ar3Bi was reported to provide the coupling products in good yields when the bromides were used in excess (Scheme 50) [65]. Under the same reaction conditions, arylation of propargyl bromide also proceeded to provide arylated allenes in moderate yields (Scheme 51) [65]. 

In 1931 Pr6vost reported the reaction of cinnamyl bromide (13) to cinnamyhnagnesium bromide (14), which was the first example of a bromine-magnesium exchange reaction (equation 10). ... 

The scope of the method turned out to be particularly broad (Table 12). The allylic substitution of cinnamyl bromide could also be performed with other linear alkyl Grignard... 

Thus, the zincated propionitrile 246 reacts with cinnamyl bromide in the presence of CuCN 2LiCl leading to the SAr2 -substitution product 247, whereas in the presence of catalytic amounts of Pd(PPh3)4 the formal SA 2-substitution product 248 is obtained... 

The enantiopure 3-amino-2-(l-hydroxyethyl)quinazolinone 258 upon alkylation with cinnamyl bromide afforded O-alkylated product 259 as minor and N,0-dialkylated product as major (Scheme 58). Further iV-acetoxylation of 259 led to the formation of 260, which underwent intramolecular aziridination to give the 1,4,5-oxadiazepine 261 as a single diastereomer <1995J(P2)205>. 

The extent of C-alkylation as a side reaction in etherification varies about 1% of allyl 2-allylphenyl ether is formed when phenol is used in the acetone and potassium carbonate method with allyl bromide with cinnamyl bromide or 7,7-dimethylallyl bromide the extent of C-alkylar tion is greater.16 A complicated mixture of C- and O-alkylation products results from the treatment of phenol with 4-bromo-2-hexene and 4-chloro-2-hexene. 9 4-Hexenylresordnol has been obtained in about 40% yield from the reaction of l-bromo-2-hexene, resorcinol, and potassium carbonate in boiling acetone.99 An appreciable amount of C-alkylation occurs when 2,6-dimethyIphenol is treated with allyl bromide and sodium ethoxide in ethanol.70 Since, in general, the ampunt of C-alkylation is greatly increased by carrying out the alkylation on the sodium salt of the phenol in benzene,16 this method is unsuitable for the preparar tion of allyl aryl ethers. 

Direct allylation of rhodanine 49 (Scheme 13) under Pd(0)-catalysis with cinnamyl ethyl carbonate affords the /V-allylated compound 50. However, allylation with cinnamyl bromide and a base is not regioselective, producing a mixture of 50 and sulfide 51. Sulfide 51 isomerizes to 50 under palladium catalysis (N > S), thus indicating that Pd(0)-catalyzed allylation of 49 is thermodynamically controlled (93T1465). 

Cinnamic acid, a-(/9-HYDROXYSTYRYL)-, y-LACTONE, 43, 3 Cinnamyl bromide, 44, 32 Condensation, of aldehydes and ketones with esters to give (S-hydroxy-esters, 44, 58... 

The reaction of benzaldehyde with unsymmetrical allylic bromides in the ionic liquid bmim also proceeds regioselectively to realize a carbon-carbon bond formation at the more substituted allylic carbon (Scheme 5). In the coupling of crotyl bromide with benzaldehyde, the product is a nearly 50 50 mixture of antilsyn diastereomers. Cinnamyl bromide predominantly gives the //-diastereomer. The regio- and diastereoselectivity is similar to that observed for these in aqueous media.104... 

Interestingly, the indium-mediated reactions of crotyl or cinnamyl bromide with aldehydes in the presence of 10 M water exclusively give the a-adducts regardless of the bulkiness of aldehydes (Scheme 6).105,106 NMR study has proved that the initially formed y-homoallylic alcohol is converted to the thermodynamic a-homoallylic alcohol. 

A /3-carboxyl group on the aldehyde also influences the diastereoselection. The high diastereoselectivity observed with the y-hydroxy lactone can be rationalized by a chelated transition state with the carboxylic acid group (Scheme 41).174 2-Oxocarboxylic acids also undergo diastereoselective allylation with cinnamyl bromide to provide the corresponding a-hydroxy acids as a single diastereomer (Equation (19)).1... 

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