Vinyl, bromo

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. 

Vapor pressure osmometric and spectroscopic studies on the molecular association and dissociation of (Z)-vinyl(bromo)-A3-iodane 130 in chloroform solution indicate the equilibrium formation of the dimer 131 as well as the iodonium ion 129, which is stabilized by the coordination of the solvent chloroform via the hypervalent interaction between the positively charged iodine and a chlorine atom [212]. 

Further evidence for the aggregation of the vinyl(bromo)-A3-iodane 130 to the dimeric form 131 was obtained from FAB mass spectrometry [212]. In the spectrum of FAB-MS of 130a, in addition to the M+ - Br peaks, prominent peaks of 2xM+- Br were observed. Furthermore, when a solution of a 1 1 mixture of... 

Equally, a 1.5 1 mixture of cis- and frans- 1,3-dibromo propene reacts with sodium dimethyl methylmalonate to furnish the vinyl bromo derivative 79 in excellent yield, which in turn is transformed in a one-pot fashion to a 1.5 1 mixture of enyne 80 or the corresponding Suzuki products 81 and 82 (Scheme 24). Interestingly, (( )-3-bromo-propenyl)-tributylstannane furnishes the vinyl stannane 83 upon allylic substitution that instantaneously is subjected to the conditions of a Stille coupling with iodo benzene to give the sequence s product 84 in 68% yield (Scheme 25). 

As was the case for 5-exo-cyclizalions, aside from the more frequently encountered substructures that undergo 6-exo-cyclization, many miscellaneous examples can be found throughout the literature [118-120]. One study concerns the effect of the stereochemistry of vinyl bromo substrates 158 and 160 on the ratio of possible double-bond isomers in the product (Scheme 6.46) [121]. Starting from the cw-compound 158, bisunsaturated indolizidinone 159 was obtained along with only traces of the bis-exo-cyclic diene. The tran -compound 160 reacted twice as fast and gave a 4 1 mixture of 161 162. Product 161 is probably the first to be formed, and its more stable isomer 162 is most likely formed by a readdition and elimination of HPdBr. 

Various pyrroles were synthesized through the ruthenium(II)-catalysed oxidative annulation of enamines with aryl- and alkyl-alkynes in r-AmOH with only 30 mol% of Cu(0Ac)2.H20 under ambient air conditions. Numerous functional groups including ester, vinyl, bromo, nitro substituents and heteroaromatic were tolerated in this catalytic system [(Eq. 96)] [184]. 

C Vinyl stannane coupling 9 3-Bromo-l-(methanesulfonyl)indole Pd(OAc)2, chloranil Z-(2-Etho,xy vinyl)tri-n-butylstannane, Pd(PPh3)2Cl2 83 [9]... 

Standard Heck conditions were used to introduce the dchydroalanine side-chain with 4-bromo-3-iodo-l-(4-methylphenylsulfonyl)indole[12]. Using 4-fluoro-3-iodo-l-(4-methylphenylsulfonyl)indole as the reactant, Merlic and Semmelhack found that addition of 2 eq, of LiCl or KCl improved yields in reactions carried out with 10% Pd/C as the catalyst[13]. The addition of the dehyroalanine side chain can also be done by stoichiometric Pd-mediated vinylation (see Section 11.2). A series of C-subslituled dehydro tryptophans was prepared in 40-60% yield by this method[14]. 

Heck type vinylation of 4-bromo-l-(4-methylphenylsulfonyl)-indole proceeds in good yield with such alkenes as methyl acrylate, styrene and N-vinylphthalimide using Pd(OAc)2 (5 mol%) and tri-o-tolylphosphine as the... 

The Suzuki coupling of arylboronic acids and aryl halides has proven to be a useful method for preparing C-aryl indoles. The indole can be used either as the halide component or as the boronic acid. 6-Bromo and 7-bromoindolc were coupled with arylboronic acids using Pd(PPh3)4[5]. No protection of the indole NH was necessary. 4-Thallated indoles couple with aryl and vinyl boronic acides in the presence of Pd(OAc)j[6]. Stille coupling between an aryl stannane and a haloindole is another option (Entry 5, Table 14.3). 

Pyrrohdinone forms alkaU metal salts by direct reaction with alkaU metals or their alkoxides or with their hydroxides under conditions in which the water of reaction is removed. The potassium salt prepared in situ serves as the catalyst for the vinylation of 2-pyrrohdinone in the commercial production of A/-vinylpyrrohdinone. The mercury salt has also been described, as have the N-bromo and N-chloro derivatives (61,62). 

The photolysis of chlorodiazirine was investigated in several cases. From chloromethyl-diazirine (232) vinyl chloride was formed as the stable primary product of stabilization of chloromethylcarbene, with acetylene and hydrogen chloride as secondary products. Some 1,1-dichloroethane was assumed to have been formed through a linear diazo compound by reaction with HCl. Added HBr yielded 1-bromo-l-chloroethane (76MI5Q800). 

Dehydrochlorination of bis(tnfluoromethylthio)acetyl chloride with calcium oxide gives bis(trifluoromethylthio)ketene [5] (equation 6) Elimination of hydrogen chloride or hydrogen bromide by means of tetrabutylammonium or potassium fluoride from vinylic chlorides or bromides leads to acetylenes or allenes [6 (equation 7) Addition of dicyclohexyl-18-crown-6 ether raises the yields of potassium fluoride-promoted elimination of hydrogen bromide from (Z)-P-bromo-p-ni-trostyrene in acetonitrile from 0 to 53-71 % In dimethyl formamide, yields increase from 28-35% to 58-68%... 

Reaction of 9-bromo-2-morphohno-4//-pyrido[l, 2-n]pyrimidin-4-ones with 4-vinylpyridine in DMF at 80 °C for 16 h in the presence of CS2CO3 and PdCbCdppf), and with amines and phenols in boiling THF for 20 h in the presence of KOr-Bu and PdCbCdppf) yielded 9-[2-(4-pyridyl)vinyl), 9-(substituted amino), and 9-aryloxy derivatives, respectively (01MIP9). 4-Hydroxyaniline gave a 9-(4-hydroxyphenyl)amino derivative. 

MMA, styrene, 2-hydroxy ethyl methyacrylate, 2-hy-droxypropyl methacrylate, acrylic and methacrylic acids, acrylamide and N-vinyl pyrrolidone (NVP) [64]. By this process, polyurethane is partially converted to N-chloro or N-bromo derivatives by a short immersion... 

Problem 13.22 3-Bromo-l-phenyl-l-propene shows a complex NMR spectrum in which the vinyli< proton at C2 is coupled with both the Cl vinylic proton (J - 16 Hz) and the C3 methylene protons (/ = 8 Hz). Draw a tree diagram for the C2 proton signal, anc account for the fact that a five-line multiplet is observed. 

It was decided to construct a D-ring acylating agent bearing a latent C-8 vinyl group. To this end, benzylation of the known 5-bromo-orr/to-vanillin (22),14 followed by protection of the aldehyde carbonyl in the form of a cyclic acetal (1,3-dioxane), affords com-... 

Benzyl alcohol, a-vinyl- [Benzene-methanol, a-ethenyl-), 106 Bcnzylamine-polystyrene [Benzene, di-ethenyl-, polymer with ethenyl-benzene, aminomethylated), 95 Benzyl bromide [Benzene, (bromo-methyl)-, 78... 

Based on the high dienophilicity of acyclic vinyl sulfones one should expect thiete dioxides to exhibit similar properties. Indeed, several Diels-Alder (2 +4) cycloadditions with thiete dioxide as dienophile are known. For example, 1,3-butadiene and 1,3-diphenylisobenzofuran react with 3-chloro- or 3-bromo-thiete dioxides to afford the corresponding 1 1 Diels-Alder cycloadducts255 277 (equation 105). 

Scheme 14 Microwave-promoted Heck vinylation of 3-bromo-2-quinolones 3.4.3...

Vinylic halides can react by a SrnI mechanism (p. 855) in some cases. An example is the FeCl2 catalyzed reaction of l-bromo-2-phenylethene and the enolate anion of pinacolone (t-BuCOCH2 ), which gave a low yield of substitution products along with alkynes. ... 

It is known that vinylic carbanions can maintain configuration, so that SeI mechanisms should produce retention there. This has been found to be the case. For example, rrans-2-bromo-2-butene was converted to 64-74% angelic acid ... 

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