O-Vinylation

Poly(vinyl chloride-i o-vinyl acetate) [9003-22-9] has found appHcation in flooring, phonograph records, protective coatings, fibers, and some films and sheeting. Because of their low viscosity and good processabihty, such copolymers constitute the bulk of the vinyl tile market. The total production of PVC copolymers in 1989 was 113,500 t (73) (see Vinyl polymers). 

Oleno synthesis via Pd catalyzed vinyl coupling o( vinyl borates with vinyl halides... 

Laudanosine contains four methoxyl groups. By exhaustive methyla-tion it yields trimethylamine and laudanosene (tetramethoxy-o-vinyl-stilbene), CH2=CH—C6H2(OCH3)2—CH=CH—C6H3(OCH3),. On oxidation with manganese dioxide and sulphuric acid it furnishes, in addition to the interesting by-product 2 3 6 7-tetramethoxy-9 10-dihydroanthracene, veratraldehyde and 4 5-dimethoxy-2 )3-methyl-... 

A number of tertiary phosphine ligands have been synthesized that also contain an alkene linkage capable of coordinating to a metal. A good example of this kind of coordination is formed in the complex of (tri-o-vinyl-phenyl)phosphine (Figure 2.29) with each alkene acting as a two-electron donor, a noble gas configuration is achieved [67],... 

Fig. 6 Microwave promoted intramolecular cyclization of o-vinyl substituted isocyanates 16 leading to 2-quinolones...

Larock has developed a new catalyst system for the Pd-catalyzed cyclization of olefinic tosylamides. Whereas typical conditions require either stoichiometric amounts of Pd(II) salts or catalytic amounts of Pd(II) in the presence of benzoquinone as a reoxidant, the new catalyst system utilizes catalytic Pd(OAc)2 under an atmosphere of O2 in DMSO with no additional reoxidant <96JOC3584>. Although o-vinylic tosylamides 76 can be cyclized to Af-tosylindoles 77 using this catalyst system, PdCla/benzoquinone is more effective for such cyclizations. Interestingly, in the case of o-allylic tosylanilides, the cyclization can be modulated to afford either dihydroindole or dihydroquinoline products. In a related approach involving a common 7i-aUyl Pd-intermediate, 2-iodoanilines were coupled with vinylic cyclopropanes or cyclobutanes in the presence of a Pd catalyst to afford dihydroindoles <96T2743>. 

Frejd and co-workers utilized a different tactic for aniline cyclization by first employing a Heck-Jeffery protocol under solvent-free conditions to prepare o-amino dehydrophenylalanine derivatives from o-aminoaryl iodides with the former undergoing a spontaneous la cyclization-elimination sequence to afford 2-methoxycarbonyl indoles <06S1183>. Dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST) was used by the Okuma group to promote the cyclization of o-vinyl-A-p-toluenesulfonylanilide to N-tosylindole <06CL1122>. 

A recent paper (160) summarizes studies involving stoichiometric hydrogenation of the olefinic link in unsaturated phosphines (e.g., o-vinyl-phenyl- or but-1-enyldiphenylphosphine) when coordinated at rhodium. 

Na2CC>3), 25 °C, 24 h. Larock extended his work in several ways [302-305], particularly with regard to Pd-catalyzed cross-coupling of o-allylic and o-vinylic anilides with vinyl halides and triflates to produce 2-vinylindoles [303-305], an example of which is shown [305]. The related "Larock indole synthesis" is discussed separately in the next section. 

From the energetically preferred n-alkyne complex there is an alternative pathway involving the hydride ligand (Figure 5). The first step is an easy (AE = 6.6 kcal.mol 1) migratory insertion of the C=C triple bond into the cis Ru-H bond to yield a a-vinyl complex, A, 10.4 kcal.mol 1 below the it-alkyne complex. This 14-electron o-vinyl complex has also a saw-horse... 

Isopropenyl acetate O Vinyl acetate O Vinyl butanoate O Vinyl octanoate 97 68... 

Acyclo-C-nucleoside analogs possessing oxazole rings were obtained from the rearrangement of lactoxime o-vinyl ethers or sugar lactoxime o-vinyl ethers [92JCS(P1)2127]. In some cases, epimerization took place at the C-2 position. 

Phenyl- and 2-(2-thienyl)-3,3-dimethyl-3//-pyrroles (58) were obtained by the reaction of the corresponding ketoximes 56 with acetylene catalyzed by MOH (M = Na, K) in DMSO. The reaction intermediate observed is the corresponding O-vinyl oxime 57 which undergoes [3,3] sigmatropic rearrangement and cyclization to products 58 (equation 24). The yield of the products obtained strongly depends on the structure of the ketoxime . 

Enehydroxylamines (102) are invoked as intermediates in the rearrangement of O-vinyl, acyl or aryl oximes (101) (equation 31). Varlamov and coworkers demonstrated that the heterocyclization of ketoximes (103) with acetylene in snper basic medium and in the presence of metal hydroxides proceeds by a [3,3]-sigmatropic rearrangement of the enehydroxylamine 105 of the corresponding oxime vinyl ethers 104 (equation 32). The unreactivity of 3-methyl-2-azabicyclo[3.3.1]nonan-9-one oxime (106) in the same reaction conditions was explained by its inability to isomerize to the corresponding enehydroxylamine. 

Fig. 3-1 Square root dependence of the polymerization rate Rp on the initiator concentration [I], — Methyl methacrylate, benzoyl peroxide, 50°C. After Schulz and Blaschke [1942] (by permission of Akademische Verlagsgesellschaft, Geest and Portig K.-G., Leipzig), o, — Vinyl benzoate, azobisisobutyronitrile, 60°C. After Santee et al. [1964] and Vrancken and Smets [1959] (by permission of Huthig and Wepf Verlag, Basel and Wiley-VCH, Weinheim).

In swine orally dosed with thiophanate, the major metabolic product in the urine was 2-aminobenzimidazole, the parent drug being present only in trace amounts. Lower levels of the 2-aminobenzimidazole glucuronide conjugate and the lobendazole metabolite were also detected. Trace amounts of thiophanate were also present in the feces, which further contained lobendazole and its 5-hydroxylated metabolite. Kidney and liver tissues were found to contain 4 metabolites, two of which were identified as the l,2,-(phenylene-bisiminocarbonothioyl)-biscarbamic acid 0-ethyl-0-(l-hydroxyethyl)ester and the (phenylene-(bisimino-carbonothioyl)) biscarbamic acid O-ethyl-O-vinyl ester. 

The oxygen analogue of the Fischer cyclization requires the formation of O-vinyl derivatives of N-aryIhydroxylarnincs. These are readily converted to indoles but are less readily accessible than the arylhydrazones used for the Fischer cyclization. 

One route to O-vinyl derivatives involves LiPdCl4-catalysed exchange with vinyl acetate[l]. Rearrangement and cyclization occur concurrently to give 1-acylindoles. 

Addition of arylhydroxylamines to electrophilic allenes such as methyl propadienoate or l-methancsulfonyl-l,2-propadiene is another route to O-vinyl derivatives[2]. The addition step is carried out by forming the salt of the hydroxylamine using NaH and the addition is catalysed with LiO,CCF3. The intermediate adducts are cyclized by warming in formic acid. Yields are typically 80% or better. 

L. Cottier, G. Remy, and G. Descotes, Photochemical synthesis of O-vinyl glycosides and their transformation into C-branched sugars, Synthesis p. 711 (1979). 

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