Vinyl derivatives preparation

Vinyl ethers are prepared in a solution process at 150—200°C with alkaH metal hydroxide catalysts (32—34), although a vapor-phase process has been reported (35). A wide variety of vinyl ethers are produced commercially. Vinyl acetate has been manufactured from acetic acid and acetylene in a vapor-phase process using zinc acetate catalyst (36,37), but ethylene is the currently preferred raw material. Vinyl derivatives of amines, amides, and mercaptans can be made similarly. A/-Vinyl-2-pyrroHdinone is a commercially important monomer prepared by vinylation of 2-pyrroHdinone using a base catalyst. 

In this application oxidative degradation of a-polymalic vinyl derivatives using potassium permanganate was used to prepare higher acid homologs... 

It was intended (85KGS1501) to find milder synthetic conditions for further simplifying the purification of 3-alkyl-2-phenylpyrroles (5,6) (Scheme 5). It was necessary to increase the DMSO content of the reaction mixture. So, when the synthesis was carried out under pressure in a 10-fold excess (of the total mass of reagents) of DMSO with an equimolar (with respect to ketoxime) amount of KOH, it was possible to decrease considerably the reaction temperature (to 50-60°) and prepare 3-alkyl-2-arylpyrroles (5) and their 1-vinyl derivatives (6) (which more readily undergo purification) in total yield up to 90%. 

The moderate yield of pyrroles 8 and 9 seems to be related to cleavage of the C—S bond (81MI4). Vinyl derivatives 10 and 11 were prepared by direct vinylation of pyrroles 8 and 9 by acetylene under atmospheric pressure (120°C, 5 hr, pyrrole/KOH molar ratio 1 5) (Scheme 8) [90ZOR(ip)]. 2-(4-Ethylthiophenyl)-l-vinylpyrrole (10) was isolated in 48% yield. 

However, recently it has been shown (88ZOR2436) that 2-aryl-3-methylpyrroles (122) can be synthesized from aryl ethyl ketoximes (121) using vinyl chloride instead of acetylene in good preparative yields (45-51%). The yield of the corresponding N-vinyl derivatives (123) is 4-6% in this case (Scheme 59). 

Oxo-4//-pyrido[l,2-a]pyrimidine-7-carboxylates 500 were obtained when 7-iodo-4T/-pyrido[ 1,2-a]pyrimidines 499 reacted with carbon monoxide in the presence of bis(triphenylphosphine)palladium(II) chloride catalyst and triethylamine (Scheme 29) (94MI2). From 7-iodo derivatives 499, 7-vinyl derivatives 501 and 7-(l-ethoxyvinyl) derivatives 502 were prepared with vinyltributyltin in the presence of Pd(PPh3)4 and with (1-ethoxy-vinyl)tributyltin in the presence of bis(triphenylphosphine)palladium(II) chloride catalyst, respectively, in toluene at 80°C. 7-(l-Ethoxy vinyl)pyr-ido[l, 2-a]pyrimidin-4-ones 502 were hydrolyzed to yield 7-acetyl derivatives 503. The acetyl group of compounds 503 was reduced with sodium borohydride in the presence of cerium(III) chloride in ethanol to give 7-(1 -hydroxyethyl)pyridopyrimidin-4-ones 504. 

Allylic phosphonium ylids have long had a valued place In the synthesis of 1,3-dienes, and similarly a-heterosubstituted ylids have been used in the preparation of vinyl derivatives ( 1). This paper is concerned with the preparation and ylid chemistry of a series of a-alkoxyallylic phosphorus derivatives which possess both the structural features alluded to above. 

This is particularly so with a-heterosubstituted derivatives, as shown by a number of recent examples in which oxide derived ylids have been found to give vinyl derivatives in circumstances where the corresponding phosphonate derived ylids do not (2-5). It was therefore decided to prepare the parent (unsubstituted) a-methoxy-allyl phosphorus compounds 1, 2 and 3, in order to investigate their Wittig-type chemistry. 

Several other examples of the utility of Pd-mediated reactions in synthesis of aryl and vinyl derivatives of pyrrole and indole were reported. Schmidt and coworkers examined arylation of 1-vinylpyrroles under Heck conditions. Reaction took place at the A-vinyl group. While the parent compound gave a mixture of -and -arylation, 2,3-dialkyl-1-vinylpyrroles preferred -substitution. <95RCB767> Grieb and Ketcha used Suzuki coupling conditions to prepare several 1-... 

Allylmetallation of vinyl lithium derivatives preparation of 4-methyloctene... 

Crotylmetallation of vinyl lithium derivatives preparation of (2S, 3S )-dimethyl-1-ferf-butoxypent-4-ene... 

If unusual vinylic tellurides or vinylic tellurides of defined stereochemistry are required, other vinyl organo-metallics are employed. In recent years, a number of methods of preparing vinylic derivatives of tellurium using organotellurium halides have been developed. 

TABLE 1. Summary of random co-vinyl acetate derivatives prepared by emulsion polymerization using ammonium persulfate as the free radical initiator. 

Dihydro-lH-benz[g]indoles 7a,b and their N-vinyl derivatives 8a,b were prepared from oximes 9a,b with acetylene and MOH-DMSO (M = Li, K) (Equation (2)) (00JOC2900). 

The oxidation of the chiral ferrocenyl vinyl selenides, prepared from the optically active diferrocenyl diselenides and ethyl propiolate derivatives, with 1 molar equivalent of MCPBA under various conditions afforded the corresponding chiral selenoxides. The chiral selenoxides suffered in situ selenoxide elimination to afford the axially chiral allenecarboxyUc esters in moderate chemical yields with high enantioselectivities (Scheme 10). Typical results are shown in Table 5. The reaction temperature had a remarkable effect upon stereoselectivity and the lower temperature gave better results. The addition of molecular sieves (4 A) to the reaction system improved the stereoselectivity. Dichlo-romethane was revealed to be the solvent of choice. In other words, reaction conditions to suppress the racemization of a diastereomeric selenoxide intermediate were required. Asymmetric selenoxide elimination provides a new method for the preparation of the chiral allenecarboxyUc esters which have so far been prepared by optical resolution of the corresponding racemic acids. 

Here lies the first roadblock. Although the large scale preparation of some related vinyl derivatives such as enol ethers from acetylene itself has been used in the chemical industry for years, these syntheses usually require catalysis by mercuric salts and yields are often quite poor. Similarly, enamines have been claimed to be intermediates in the synthesis of amines from alkynes, but this process also requires mercuric ion catalysis. ... 

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