Alkene derivatives vinylation

Chiral alkenes derived from ot,p-unsaturated aldehydes have also been applied in asymmetric 1,3-dipolar cycloadditions (142). Soucy et al. (142) used (—)-8-(benzylamino)menthol (94) and acrolein for the exclusive formation of 95 having an equatorial C(2) vinyl group (Scheme 12.31). The 1,3-dipolar cycloaddition of acetonitrile oxide with 95 gave 96 with a selectivity of > 90% de. 

Carbolithiation reactions of ketone a,-dianions, generated by the above amine-free method with several alkenes, such as styrenyl derivatives, vinyl sulfides and vinylsilanes, can lead to the generation of ketone a,5-dianions (Scheme 15)14. For example, when one equivalents of triphenylvinylsilane was treated with a ketone a,-dianion, in THF, at 0 C for 1 h and the resulting reaction mixture was quenched by 2.2 mol equivalents of trimethylchlorosilane, the corresponding bis-silylated enol silyl ether was obtained. Substituted styrenyl derivatives, such as 1,1-diphenylethylene and cinnamyl alcohol, also underwent a smooth carbolithiation to give the corresponding ketone a,5-dianions. Similar addition reactions of ketone a,f)-dianions to vinyl phenyl sulfide took place smoothly to give a,5-dianions with a sulfur attached in the 5-position. 

For historical reasons, there are a few alkenes whose names are firmly entrenched jn common usage but don t conform to the rules. For example, the alkene derived from ethane should be called ethene, but the name ethylene has been used so long that it is accepted by lUPAC. Table 6.1 lists several other common names that are often used and are recognized by lUPAC. Note also that a =CH2 substituent is called a methylene group, a H2C=CH substituent is called a vinyl group, and a H2C=CHCH2- substituent is called an allyl group ... 

A variety of pyridine ring syntheses stem from Vilsmeier formylation of alkenes, enamines, vinyl ethers, ketones, and related systems followed by a separate cyclization of the derived salts with ammonium chloride or acetate.49... 

The parent dibromide 9 (R = H) also underwent ring opening at ambient temperature and was trapped with 2,3-dimethylbut-2-ene or methyl 2-methylacrylate. A full account of the ring opening of 3-benzyl-l,2-dichloro-3-methylcyclopropcne and trapping of the derived vinyl-carbene by alkenes is also available. ... 

The synthesis of vinylphosphonate-linked nucleotide dimer (93) has been achieved using an olefin-metathesis reaction step between the vinylphosphonate (91) and the 5 -alkene derivative of thymidine (92). The second-generation Grubb s catalyst was reported to be the superior catalyst for this conversion in which no vinyl phosphonate homo-coupling was detected. ... 

To get back to tartaric acid from 186 we must disconnect as in 186a and the obvious synthon is 187 with the proviso that the nucleophilic end must control the geometry of the alkene. A vinyl silane is a good answer (chapter 18) with some leaving group at the other end 188 together with the imide 189 obviously derived from tartaric acid 35. 

The range of applicability of the Wittig reaction has in recent years become extremely extensive and there have been reports of its use for the preparation of alkyl- and aryl-substituted alkenes, unsaturated aldehydes, ketones, and carboxylic acid derivatives, vinyl halides, and vinyl ethers. In the preparation of these compounds there is often the possibility of cis-trans isomerism Bestmann and Kratzer1003 state that the trans-olefin is always obtained when an alkylidenetricyclohexylphosphorane is used, and Schlosser and Christ-... 

Alkene derivatives such as alkenylboronic acids and alkenylzir-conanes reacht with PhI(OAc)2 to furnish alkenyliodonium salts (eq 46). These transformations proceed with retention of olefin configuration. Similarly, alkenylboron species add to PhI(OAc)2 in the presence of Nal to give vinyl acetate products (eq 47). In these examples, ( )-alkenylboronates give stereochemically pure (Z)-configured enol acetates. ... 

Only one previous method exists for the replacement of a -hydrogen atom of a conjugated enone by an electrophilic substituent. Now treatment of aj8-unsaturated aldehydes and ketones with triphenylthioborate has been shown to provide 1,3-bis(phenylthio)alkene derivatives, the anions of which are effective /S-acyl vinyl anion equivalents (Scheme 51). ... 

Alkyne complexes of low oxidation state metals react with electrophiles generally to produce alkene derivatives resulting from addition of the electrophilic species to the coordinated triple bond. These reactions often proceed by way of (x-vinyl-metal derivatives, and in several cases such intermediates have been isolated. The vinyl complexes, in turn, may be cleaved in a subsequent reaction to afford substituted alkenes [Eq. (29)]. 

In addition to benzene and naphthalene derivatives, heteroaromatic compounds such as ferrocene[232, furan, thiophene, selenophene[233,234], and cyclobutadiene iron carbonyl complexpSS] react with alkenes to give vinyl heterocydes. The ease of the reaction of styrene with sub.stituted benzenes to give stilbene derivatives 260 increases in the order benzene < naphthalene < ferrocene < furan. The effect of substituents in this reaction is similar to that in the electrophilic aromatic substitution reactions[236]. 

Thallation of aromatic compounds with thallium tris(trifluoroacetate) proceeds more easily than mercuration. Transmetallation of organothallium compounds with Pd(II) is used for synthetic purposes. The reaction of alkenes with arylthallium compounds in the presence of Pd(Il) salt gives styrene derivatives (433). The reaction can be made catalytic by use of CuCl7[393,394], The aryla-tion of methyl vinyl ketone was carried out with the arylthallium compound 434[395]. The /9-alkoxythallium compound 435, obtained by oxythallation of styrene, is converted into acetophenone by the treatment with PdCh[396]. 

Depending on the substituents of l,6-enynes, their cyclization leads to 1.2-dialkylidene derivatives (or a 1.3-diene system). For example, cyclization of the 1,6-enyne 50 affords the 1.3-diene system 51[33-35]. Furthermore, the 1.6-enyne 53, which has a terminal alkene, undergoes cyclization with a shift of vinylic hydrogen to generate the 1,3-diene system 54. The carbapenem skeleton 56 has been synthesized based on the cyclization of the functionalized 1,6-enyne 55[36], Similarly, the cyclization of the 1,7-enyne 57 gives a si -mem-bered ring 58 with the 1,3-diene system. 

The cyclohexadiene derivative 130 was obtained by the co-cyclization of DMAD with strained alkenes such as norbornene catalyzed by 75[63], However, the linear 2 1 adduct 131 of an alkene and DMAD was obtained selectively using bis(maleic anhydride)(norbornene)palladium (124)[64] as a cat-alyst[65], A similar reaction of allyl alcohol with DMAD is catalyzed by the catalyst 123 to give the linear adducts 132 and 133[66], Reaction of a vinyl ether with DMAD gives the cyclopentene derivatives 134 and 135 as 2 I adducts, and a cyclooctadiene derivative, although the selectivity is not high[67]. 

The Hegedus indole synthesis involves one of the earlier (formal) examples of olefin hydroamination. An ortho-vinyl or ortho-nllyl aniline derivative 1 is treated with palladium(II) to deliver an intermediate resulting from alkene aminopalladation. Subsequent reduction and/or isomerization steps then provide the indoline or indole unit 2, respectively. 

The reactions of nitrones constitute the absolute majority of metal-catalyzed asymmetric 1,3-dipolar cycloaddition reactions. Boron, aluminum, titanium, copper and palladium catalysts have been tested for the inverse electron-demand 1,3-dipolar cycloaddition reaction of nitrones with electron-rich alkenes. Fair enantioselectivities of up to 79% ee were obtained with oxazaborolidinone catalysts. However, the AlMe-3,3 -Ar-BINOL complexes proved to be superior for reactions of both acyclic and cyclic nitrones and more than >99% ee was obtained in some reactions. The Cu(OTf)2-BOX catalyst was efficient for reactions of the glyoxylate-derived nitrones with vinyl ethers and enantioselectivities of up to 93% ee were obtained. 

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