Vinyl Halogenides

The first trials to hydroformylate vinyl chloride were conducted with unmodified cobalt catalysts [9]. At 90-110°C and 200 bar syngas pressure, by applying a slight excess of CO (H2/CO = 1.35) up to 90% 2-chloropropionaldehyde was produced within 90 min. At higher temperatures. 

Acyclic and Cyclic Vinyl Ethers, Vinyl Acetates, and Vinyl Carbonates 

The preference for the formation of the a-isomer in rhodium-catalyzed hydroformylation can be enhanced by lowering the temperature [16]. Also, aryl ether groups (aryl = phenyl, naphthyl) support this regioselectivity, but may also slow down the conversion. 

The hydroformylation of 2,3-dihydrofuran and 3,4-dihydro-2//-pyran can be accompanied by partial isomerization to the isomeric cyclic allyl ethers. In general, dihydrofurans as substrates require conditions milder than those used for dihydropyrans, which has been explained by the more planar structure of the five-membered ring that facilitates the formation of substrate-metal complexes [17]. 

The idea of producing lactic acid and alkyl lactates by hydroformylation of vinyl acetate was first patented by Monsanto in 1975, using a phosphine complex of rhodium as a catalyst [36]. Also, Kuraray has shown interest in this route [37], which covers three steps, namely, hydroformylation, subsequent oxidation, and final hydrolysis or alcoholysis. 

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Natrinm-flnoro-tiihydrido-borat reduziert Vinyl-halogenide selektiv zu Olefinen (S. 400). Es wird aus Di-boran und Natriumfluorid hergestellt. 

Auch Briickenkopf-Halogen-Atome sowie Halogen-aromaten, Vinyl-halogenide usw. werden mit uberschiissigem Lithiumalanat bei geniigend hohen Reaktionstemperaturen zu Kohlenwasserstoffen reduziert4. 

Vinyl-halogenide lassen sich in der Regel mit Organo-zinnhydriden nur schwierig dehalogenieren6,1. 

For the preparation of aryl or heteroaryl acetylenic compounds, the reactions proceed in good yield, with little isomerization of the products. When a two-step process is used, a highly stable vinyl halogenide forms in the first step under mild conditions. Dehalogenation with a strong base in the second step yields the corresponding alkynes [Eqs. (1 8)]. 

Poly(vinyl ether)s, Poly(vinyl ester)s, and Poly(vinyl halogenide)s... 

It is, for example, known that the dehydrohalogenation of vinyl halogenides XXVIII proceeds preferably by the mechanism of trans-elimination. The stereoselectivity can be explained as follows [84]. The structure of bent acetylene emerging upon trans-elimination of the hydrohalogen elements transforms much more readily into an equilibrium linear form than the structure forming in the case of a cis-elimination. The frequency of the symmetrical normal vibration Ttg, which corresponds to the deformations of XXIX, equals 612cm" which is much less than the value of 729 cm for the antisymmetrical vibration 7c of the structure XXX ... 

The direction of reaction associated with the minimal deformation energy is considered preferable. The changes in the coordiates qi corresponding to the values of permit conclusions to be drawn as to the reaction path and reaction coordinate. For example, in the case of the dehydrohalogenation of vinyl halogenides XXVIII considered earlier the calculated value of for trans-elimination of hydrohalogenide amounts to 0.32 A (/, = 1), while for the cis-elimination it is 1.24 A whence a conclusion may be made in favor of the former direction. 

As many of the selectivity problems in this field can be solved vwth quite simple techniques - for example, using the very different reactivity data in this group of elements or making use of halophilic cations as catalysts - we restrict ourselves here to vinyl halogenides. 

In contrast to these concepts above obtained from numerous ab-initio molecular orbital calculations (usually from small radicals, e. g. H, F, H3C or HOCH2 to fluoroalkenes), some semi-empirical calculation on more longer halogenated radicals were performed by Rozhkov et al. [333, 334] and Xu et al. [335]. The former team determined equilibrium geometries and electronic properties of perfluoroalkyl halogenides and showed that fluorine atoms in vinyl position strongly stabilise all the sigma molecular orbital. 

Aus (l-Halogen-ethyl)-phosphinsaure-chloriden erhalt man dagegen keine Vinyl-phos-phinsaure-halogenide wie folgendes Beispiel zeigt315 ... 

PT are also active in lubricating oils and vinylic monomers. Multicomponent mixtures comprising HAS 28 (R = H), PT 20 and DPA 9a or a phenolic AO were proposed as antiwear additives for lubricating oils. PNA or dinaphthyl-PD provide excellent thermostability and suppress discoloration of PUR or PE doped with halogenated FR. Any negative influence of potentially released hydrogen halogenides from FR on amines was observed in these combinations. 

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