By dehalogenation

Semicommercial production of 3,3/4,4 -biphenyltetracarboxyhc dianhydride [2420-87-3] in the United States has been announced by Occidental Chemical Corp. (74). This polyimide resin intermediate is prepared by dehalogenative dimerization of 4-chlorophthalate salts (75) or by oxidative coupling of phthalate esters (76). 

A quite different structural motif is found in the curious cyclic hexamer [(BNMc2)6] which can be obtained as orange-red crystals by distilling the initial product formed by dehalogenation of (Me2N)2BCl with Na/K alloy ( >... 

Ketenes can be prepared by dehalogenation of a-halo acyl halides with zinc or with... 

Compounds of the type E(IXE(III)R2] that are analogous to the group-IA-group-IVB compounds, e.g., LiSnPh3, should be given by dehalogenation of diorganometal halides ... 

The addition of a vinyl radical to a double bond is usually favorable thermodynamically because a more stable alkyl radical is formed. The vinyl radical can be generated by dehalogenation of vinyl bromides or iodides. An early study provided examples of both five-and six-membered rings being formed.329 The six-membered ring is favored when a branching substituent is introduced. 

The procedure described is essentially that of Ballard and Dehn.1 Stilbene has also been prepared by reduction of desoxy-benzoin,20 benzaldehyde,23 and benzil 2o-2c by dehydrogenation of ethyl benzene,30 toluene,30- 33- 3, and bibenzyl 33-3alkaline reduction of phenylnitromethane,40 phenylnitroacetonitrile,40 and desoxybenzoin 43 by distillation of benzyl sulfone,50 benzyl sulfide,60-63 calcium cinnamate,5 cinnamic acid,5d phenyl cinna-mate,6e-6/ and diphenyl fumarate ie by dehydrohalogenation of a,a -dichlorobibenzyl60 and benzyl chloride 63 by dehalogenation of a,a,c/,a -tetrachlorobibenzyl70 and benzal chloride 73 by the coupling of cinnamic acid and phenyldiazonium chloride 8 by de-... 

Planar 30a is obtained by dehalogenation of 29a [42], Upon heating, 30a rearranges to the folded 1,3-diborete 28a. Its X-ray structure analysis revealed the shortest transannular C-C distance (174 pm) in l,3-dihydro-l,3-diboretes [43],... 

Hexahydropyrido[l,2-6]pyridazin-8-ones 178 and a 2,3-tetramethylene derivative were formed on the intramolecular cycloaddition of 177, formed in situ by dehalogenation of hydrazones of the hex-5-enoic acid derivatives 176 [87JCS(P1)2511]. Intramolecular cycloaddition of hydrazones 179 in... 

Reaction of o-iodobenzenesulfonamide 265 with the potassium enolate of ketones 266 in liquid ammonia under photochemical conditions affords 1,2-benzothiazine 1,1-dioxides 267 in excellent yield (Scheme 37) <2005JOC9147>. While a variety of other ketone substrates have been investigated for this reaction, those containing /3-hydrogens afford significant amounts of benzenesulfonamide by dehalogenation of the starting material 265. 

Condensing 131 with 132 in acetonitrile in the presence of powdered KOH and tris[2-(2-methoxyethoxy)ethyl]-amine (TDA-1) for 20 min at room temperature resulted in formation of 133 <2003JOC5519> along with 134 and a trace amount of 135. Note that formation of an N-2-isomeric glycoside was not accompanied by dehalogenation, which is different to a closely related glycosylation procedure for 131 (Equation 4) <1998S207>. 

Chlorodifluorothioacetyl fluoride prepared by this reaction has a boiling point of 23° C. NMR characterization of this compound gave a low-field triplet and high-field doublet in a ratio of 1 2, as would be expected. However, a material boiling at 36° C had been reported earlier as chlorodifluorothioacetyl fluoride (54). This material was obtained by dehalogenation erf 2-chlorotetrafluoroethane-sulfenyl chloride with tin. In view of... 

The intermolecular Heck reactions of oxazoles and thiazoles with olefins are not too common. They are rarely high yielding since in several cases they are biased by dehalogenation. Due to this reason the olefination of these systems is usually achieved through Stille coupling with vinylstannanes. 

Ketenes can be prepared by dehalogenation of ot-halo acyl halides with zinc or with tri-phenylphosphine.348 The reaction generally gives good results when the two R groups are aryl or alkyl, but not when either one is hydrogen.34,1 OS IV, 348 68, 41. 

In some cases, especially when alkynes are prepared by dehalogenations of haloalkenes, the intermediate organometallic compounds, depending on the nature of the metal, are sufficiently stable to be identified or even isolated at ambient temperatures. This property can be exploited in transmetalation reactions with suitable organometallic compounds, and thus new polylluorinated organometallic species may be prepared. 

Table 4. Formation of Fluorinated Unsaturated Alicyclic Compounds by Dehalogenation...

Aryl-aliphatic compounds which are formed by dehalogenation in a side chain attached to an aromatic ring, or to the alicyclic ring of benzocycloalkenes, arc presented in Table 6. Such... 

Fluorinated unsaturated alcohols have been prepared from the point of view of potential fluo-rinated monomers with a reactive pendant group. There seem to be no examples of the preparation of fluorinated unsaturated phenols by dehalogenation. Examples of the formation of fluorinated unsaturated alcohols are listed in Table 7. 

Table 9. Formation of Unsaturaled Fluorinated Ketones, and Fluorinated Ketenes. by Dehalogenation...

Fluorinated unsaturated carboxylic acids and their functional derivatives are prospective monomers for polymerization reactions. Their preparation fully relies on dehalogenation procedures dechlorination, and debromo- and dechlorofluorination are mostly employed (see Table 10). Fluorinated unsaturated acid halides can be prepared by dehalogenations with zinc46-61 or copper121 in aprotic solvents. 

Organocopper reagents, 207 Organovanadium reagents, 219 By desilylation of vinylsilanes Tetrabutylammonium fluoride, 286 By desulfurization of vinyl sulfides and related sulfur compounds Sodium dithionite, 281 Elimination reactions By dehalogenation Dichlorobis(cyclopentadienyl)-titanium, 102... 

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