Mercury vinylations

NESHAPs). Between 1970 and 1989, standards were promulgated for asbestos, beryllium, mercury, vinyl chloride, benzene, arsenic, radionuclides, and coke-oven emissions. 

Using bromodichloromethyl(phenyl)mercury, vinyl acetate afforded 2-acetoxy-l,l-dichlo-rocyclopropane (1, 85%), dichlorocyclopropanation of other aldehyde enol esters would also be expected. The cyclopropane 1 ( 10%) together with 2-acetoxy-l,l,l-trichloropropane (2,10%) were formed when the dichlorocarbene was generated from sodium trichloroacetate, the chain product 2 results from the reaction of the trichloromethyl anion (for the mechanism, see ref 197). These reactions are described in Houben-Weyl, Vol. 4/3, pp 177-178. Under phase-transfer catalytic conditions (CHClj/base/PTC), with a typical catalyst such as benzyl-triethylammonium chloride, vinyl acetate gave 2 (65%) only (Houben-Weyl, Vol.E19b, ppl550-1551). 

The National Emission Standards for Hazardous Air Pollutants (NESHAPS) specify emission standards for various hazardous air pollutants and cover asbestos, arsenic, benzene, beryllium, mercury, vinyl chloride, PVC, etc. 

A hazardous air pollutant is one for which no ambient air-quality standard is applicable, but which may cause or contribute to increased mortality or illness in the general population. Emission standards for such pollutants are required to be set at levels that protect the public health. These allowable pollutants emission levels are known as NESHAPS and include levels for radon-222, beryllium, mercury, vinyl chloride, radionuclides, benzene, asbestos, arsenic, and fugitive organic leaks from equipment. 

There also exists an acidregioselective condensation of the aldol type, namely the Mannich reaction (B. Reichert, 1959 H. Hellmann, 1960 see also p. 291f.). The condensation of secondary amines with aldehydes yields Immonium salts, which react with ketones to give 3-amino ketones (=Mannich bases). Ketones with two enolizable CHj-groupings may form 1,5-diamino-3-pentanones, but monosubstitution products can always be obtained in high yield. Unsymmetrical ketones react preferentially at the most highly substituted carbon atom. Sterical hindrance can reverse this regioselectivity. Thermal elimination of amines leads to the a,)3-unsaturated ketone. Another efficient pathway to vinyl ketones starts with the addition of terminal alkynes to immonium salts. On mercury(ll) catalyzed hydration the product is converted to the Mannich base (H. Smith, 1964). 

The reaction of alkenyl mercurials with alkenes forms 7r-allylpalladium intermediates by the rearrangement of Pd via the elimination of H—Pd—Cl and its reverse readdition. Further transformations such as trapping with nucleophiles or elimination form conjugated dienes[379]. The 7r-allylpalladium intermediate 418 formed from 3-butenoic acid reacts intramolecularly with carboxylic acid to yield the 7-vinyl-7-laCtone 4I9[380], The /i,7-titisaturated amide 421 is obtained by the reaction of 4-vinyl-2-azetidinone (420) with an organomercur-ial. Similarly homoallylic alcohols are obtained from vinylic oxetanes[381]. 

The stereo-defined enol ester 432 is prepared by the reaction of the vinyl-mercurial 431, obtained by acetoxymercuration of 2-butyne. with mercury(II) carboxylates using a catalytic amount of Pd(OAc)2[392]. 

Liquid- and vapor-phase processes have been described the latter appear to be advantageous. Supported cadmium, zinc, or mercury salts are used as catalysts. In 1963 it was estimated that 85% of U.S. vinyl acetate capacity was based on acetylene, but it has been completely replaced since about 1982 by newer technology using oxidative addition of acetic acid to ethylene (2) (see Vinyl polymers). In western Europe production of vinyl acetate from acetylene stiU remains a significant commercial route. 

Automated analyzers may be used for continuous monitoring of ambient poUutants and EPA has developed continuous procedures (23) as alternatives to the referenced methods. Eor source sampling, EPA has specified extractive sampling trains and analytical methods for poUutants such as SO2 and SO [7446-11-9] sulfuric acid [7664-93-9] mists, NO, mercury [7439-97-6], beryUium [7440-41-7], vinyl chloride, and VOCs (volatile organic compounds). Some EPA New Source Performance Standards requite continuous monitors on specified sources. 

Vinyl acetate (ethenyl acetate) is produced in the vapor-phase reaction at 180—200°C of acetylene and acetic acid over a cadmium, 2inc, or mercury acetate catalyst. However, the palladium-cataly2ed reaction of ethylene and acetic acid has displaced most of the commercial acetylene-based units (see Acetylene-DERIVED chemicals Vinyl polymers). Current production is dependent on the use of low cost by-product acetylene from ethylene plants or from low cost hydrocarbon feeds. 

Catalysts. Mercury is or has been used in the catalysis (qv) of various plastics, including polyurethane [26778-67-6] poly(vinyl chloride) [9002-86-2] and poly(vinyl acetate) [9003-20-7]. Most poly(vinyl chloride) and poly(vinyl acetate) is manufactured by processes that do not use mercury (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). 

Benzo[h]thiophene sulfone (229) reacts as a vinyl sulfone and forms adducts (228) and (230) when treated with mercury(II) acetate in methanol and with cyclopentadiene, respectively. 

The hazards of chemicals are commonly detected in the workplace first, because exposure levels there are higher than in the general environment. In addition, the exposed population is well known, which allows early detection of the association between deleterious health effects and the exposure. The toxic effects of some chemicals, such as mercury compounds and soot, have been known already for centuries. Already at the end of the eighteenth century, small boys who were employed to climb up the inside of chimneys to clean them suffered from a cancer of the scrotum due to exposure to soot. This was the first occupational cancer ever identified. In the viscose industry, exposure to carbon disulfide was already known to cause psychoses among exposed workers during the nineteenth century. As late as the 1970s, vinyl chloride was found to induce angiosarcoma of the liver, a tumor that was practically unknown in ocher instances. ... 

Vinyl acetate was originally produced hy the reaction of acetylene and acetic acid in the presence of mercury(II) acetate. Currently, it is produced hy the catalytic oxidation of ethylene with oxygen, with acetic acid as a reactant and palladium as the catalyst ... 

O The alkyne uses a pair of electrons to attack the electrophilic mercury(II) ion, yielding a mercury-containing vinylic carbocation intermediate. 

The chemistry of alkynes is dominated by electrophilic addition reactions, similar to those of alkenes. Alkynes react with HBr and HC1 to yield vinylic halides and with Br2 and Cl2 to yield 1,2-dihalides (vicinal dihalides). Alkynes can be hydrated by reaction with aqueous sulfuric acid in the presence of mercury(ll) catalyst. The reaction leads to an intermediate enol that immediately isomerizes to yield a ketone tautomer. Since the addition reaction occurs with Markovnikov regiochemistry, a methyl ketone is produced from a terminal alkyne. Alternatively, hydroboration/oxidation of a terminal alkyne yields an aldehyde. 

With trifluoromethanesulfonic acid, all four vinyl groups are displaced at - 78°, to give a compound that was shown by Mossbauer spectroscopy to contain both Sn(II) and Sn(IV), and that was assigned the formula Sn [Sn (S03CF3)6]. Trivinyltin carboxylates have also been prepared from the reaction between tet avinyltin and mercury(I) carboxylates, which may be generated electrochemically in situ (185). 

The reaction has also been used to prepare 1,3-dilithiopropanes" and 1,1-dilithio-methylenecyclohexane" from the corresponding mercury compounds. In general, the equilibrium lies in the direction in which the more electropositive metal is bonded to that alkyl or aryl group that is the more stable carbanion (p. 228). The reaction proceeds with retention of configuration an Sgi mechanism is likely. Higher order cuprates (see Ref. 1277 in Chapter 10) have been produced by this reaction starting with a vinylic tin compound ... 

Triple bonds can give enol esters or acylals when treated with carboxylic acids. Mercuric salts are usually catalysts, and vinylic mercury compounds... 

The organo-corrinoids show similar behavior, but also additional complications. Rate constants have been determined 84) for the attack of mercury(II) acetate on various organocobalt cobinamides (X = H2O or absent) and cobalamins (X = 5,6-dimethylbenziminazole). The first complication, which has to be born in mind when comparing the cobinamides with the cobalamins or DMG complexes, is that the organocobin-amides are partly (R = vinyl and methyl) or wholly (R = Et, -Pr, t-Pr,... 

Reagent (12) was used for synthon (10), though no doubt bromoacetone would also add to the enamine ol (11). Mercury catalysed hydrolysis oJ vinyl chloride released (9) which duly cyclised to (8) in base. Synthesis ... 

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