Oxalyl bromide chloride

Surface-mediated addition of HC1 or HBr can be carried out in the presence of silica or alumina.150 The hydrogen halides can be generated from thionyl chloride, oxalyl chloride, oxalyl bromide, phosphorus tribromide, or acetyl bromide. The kinetic products from HC1 and 1-phenylpropyne result from syn addition, but isomerization to the more stable Z-isomer occurs upon continued exposure to the acidic conditions. 

Experimental support for the above analysis of 2,3-disubstituted 1,3-dienes is available. For example, 2,3-dichlorobutadiene has been shown to exist preferentially in a planar tram geometry 20S A more interesting case is the conformational isomerism exhibited by oxalyl bromide and chloride. It is found that in the gas phase, these molecules exist in an equilibrium mixture of tram and gauche isomers but no detectable concentration of the cis conformation was observed206, 207 ... 

The existence of a large concentration of the gauche conformation implies that pi nonbonded interactions of the type discussed previously play some role in the conformational isomerism of oxalyl bromide and chloride. 

Interchange of halogen is a means of synthesis of certain acyl halides which cannot be conveniently prepared by other methods. Acetyl fluoride is made from acetyl chloride and sodium hydrogen fluoride in acetic anhydride solution." By passing a stream of hydrogen bromide through oxalyl chloride an 85% yield of oxalyl bromide, (COBr), is obtained. The bromide cannot be made by the action of phosphorus pentabromide on oxalic acid. The method has also been applied to the preparation of acetyl bromide and iodide and other acyl iodides. ... 

Oxalyl chloride, (COCl), and oxalyl bromide are similarly used to make acyl chlorides and bromides in excellent yield. The only other products of these reactions are the gases hydrogen halide, carbon monoxide, and carbon dioxide. For the preparation of acyl bromides, sodium salts rather than the free acids have been treated with oxalyl bromide. This procedure requires a smaller excess of reagent. 

Finally, among the various acyl halogen compounds, formyl fluoride, oxalyl chloride, oxalyl bromide, etc., are interesting possibilities as war gases. 

Oxalyl bromide, (COBr), has been obtained by the action of hydrobromic acid on oxalyl chloride. Heat decomposes it with production of carbon monoxide and carbonyl bromide. It reacts easily with water forming carbon monoxide, carbon dioxide and hydrobromic acid. 

A mild, and often superior reagent is oxalyl chloride (113) and oxalyl bromide, since oxalic acid decomposes to CO and CO2, and the equihbrium is thus driven to the side of the other acyl hahde. These reagents are commonly the reagent of choice, particularly when sensitive functionahty is present elsewhere in the molecule. 

Figure 2 Energy profiles along the torsional angle of oxalyl fluoride (- -), oxalyl chloride (—) and oxalyl bromide ( )...

Figure 2 displays the energy profiles of the trans cis rotational isomerization of oxalyl fluoride, oxalyl chloride, and oxalyl bromide. 

For all molecules the cis conformation is the absolute minimum, whereas the trans conformation is either a secondary minimum (oxalyl fluoride) or a maximum (oxalyl chloride and oxalyl bromide). Oxalyl bromide presents a shallow minimum corresponding to a gauche conformer. Substituting F by Cl yields a cusp catastrophe which changes the two maxima at tt/2 and the minimum at 0 into a maximum at 0. The substitution of Cl by Br is responsible for a dual-fold catastrophe in which two wandering points near 27t/3 give rise to a new minimum (gauche conformation) and a new maximum. 

Acetylthio-l,2-dithioIylium salts have been described.116 A variety of methods are available for the preparation of 3-halides. The reaction of oxalyl chloride with l,2-dithiol-3-ones gives 3-chloro-l,2-dithiolylium salts (66)116 (Scheme 6). In some cases the reaction can be realized with 1,2-dithiole-3-thiones too. Phosgene can be used instead of oxalyl chloride. Oxalyl bromide gives the corresponding 3-bromo-l,2-dithiolylium salts.117 3-Chloro-l,2-dithiolylium dichlorophosphates have been prepared from 1,2-dithiol-3-ones and phosphorus oxychloride.118 The corresponding... 

Oxalic acid, 15-16, 80, 764-767,1013 Oxalyl bromide, 767 Oxalyl chloride, 28, 29, 286, 767-772 Oxanthrone acetate, 543, 545 Oxasteroids, 201 Oxaziranes, 788 OxaioUdlnei, 379 Ouwlidonn, 748... 

Oxalyl bromide, b.p. 102-103°/720 mm, is obtained in 85% yield by passing HBr [8 moles per mole of (COCl)2] into pure oxalyl chloride (100 g) for about 12 h and, after a further 6 h, fractionating the mixture. Discoloration due to bromine is removed by shaking with mercury.1109... 

Further, oxalyl bromide (or the chloride), at low temperature in the absence of a catalyst, gives very good yields of the very reactive oc-oxo carbonyl bromides ... 

Acid chlorides are commonly made from acids by exchange with an excess of thionyl chloride or oxalyl chloride. Brief heating gives the acid chloride plus gaseous by-products (Eq. 6.14) [20]. Phosphorus tri- and pentachlorides are used similarly. The acid bromides are made with phosphorus tribromide or oxalyl bromide [20]. 

Reaction of (S)-(+)-2-aminobutyrate hydrochloride with ethyl oxalyl chloride followed by replacing of the ethyl ester with amino alcohol, oxidation with Dess-Martin periodinate and cyclization using TFA/TFAA in acetic acid gave the cyclic product, which was further converted to the bromide. Sub-... 

DMSO or other sulfoxides react with trimethylchlorosilanes (TCS) 14 or trimefhylsilyl bromide 16, via 789, to give the Sila-Pummerer product 1275. Rearrangement of 789 and further reaction with TCS 14 affords, with elimination of HMDSO 7 and via 1276 and 1277, methanesulfenyl chloride 1278, which is also accessible by chlorination of dimethyldisulfide, by treatment of DMSO with Me2SiCl2 48, with formation of silicon oil 56, or by reaction of DMSO with oxalyl chloride, whereupon CO and CO2 is evolved (cf also Section 8.2.2). On heating equimolar amounts of primary or secondary alcohols with DMSO and TCS 14 in benzene, formaldehyde acetals are formed in 76-96% yield [67]. Thus reaction of -butanol with DMSO and TCS 14 gives, via intermediate 1275 and the mixed acetal 1279, formaldehyde di-n-butyl acetal 1280 in 81% yield and methyl mercaptan (Scheme 8.26). Most importantly, use of DMSO-Dg furnishes acetals in which the 0,0 -methylene group is deuter-ated. Benzyl alcohol, however, affords, under these reaction conditions, 93% diben-zyl ether 1817 and no acetal [67]. 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

Diethyl 7V-(t-butoxycarbonyl)phosphoramidate 18 is obtained from diethyl phospho-ramidate by successive treatment with oxalyl chloride and t-butyl alcohol. It forms a stable non-hydroscopic sodium salt, which reacts with a variety of alkyl halides in benzene in the presence of tetrabutylammonium bromide under phase-transfer conditions to give the corresponding TV-alkyl derivatives. The latter are cleaved by hydrogen chloride in benzene to yield amine hydrochlorides (equation 16)48. 

In the following year, this method was also applied to the total synthesis of tjipanazole FI (371) (784). For this synthesis, the required bisindole 1444 was obtained starting from 5-chloroindole (1440) in three steps and 47% overall yield. Acylation of 1440 with oxalyl chloride led to the glyoxylic acid chloride 1441. Transmetalation of indolylmagnesium bromide with zinc chloride, followed by addition of the acid chloride, provided the ot-diketone 1443. Exhaustive reduction of 1443 with lithium aluminum hydride (LiAlFl4) afforded the corresponding bisindolylethane 1444. Executing a similar reaction sequence as shown for the synthesis of tjipanazole F2 (372) (see Scheme 5.243), the chloroindoline (+ )-1445 was transformed to tjipanazole FI (371) in two steps and 50% overall yield (784) (Scheme 5.244). 

---