1,2-Dichloroethane, synthesis

Figure 2.33 Dependence of the cooling zone length L ggi) on reactor radius R. Neutralisation process (Ap = 204 kg/m ) (1,2) dichloroethane synthesis (AP =...

Ethylenediamine is produced technically by two different routes The reaction of ammonia with dichloroethane [route (d) in Topic 5.3.4 for dichloroethane synthesis, see also Section 5.3.3.9] is still the most important production route. However, in this process 2 kg of NaCl is produced as stoichiometric coupling product per kg of ethylenediamine. For this reason an alternative process has been developed that converts ethanolamine and ammonia into ethylenediamine. Ethanolamine is obtained by reaction of ethylene oxide with ammonia. 

There are three general methods of interest for the preparation of vinyl chloride, one for laboratory synthesis and the other two for commercial production. Vinyl chloride (a gas boiling at -14°C) is most conveniently prepared in the laboratory by the addition of ethylene dichloride (1,2-dichloroethane) in drops on to a warm 10% solution of sodium hydroxide or potassium hydroxide in a 1 1 ethyl alcohol-water mixture Figure 12.1). At one time this method was of commercial interest. It does, however, suffer from the disadvantage that half the chlorine of the ethylene dichloride is consumed in the manufacture of common salt. 

Beaded acrylamide resins (28) are generally produced by w/o inverse-suspension polymerization. This involves the dispersion of an aqueous solution of the monomer and an initiator (e.g., ammonium peroxodisulfates) with a droplet stabilizer such as carboxymethylcellulose or cellulose acetate butyrate in an immiscible liquid (the oil phase), such as 1,2-dichloroethane, toluene, or a liquid paraffin. A polymerization catalyst, usually tetramethylethylenediamine, may also be added to the monomer mixture. The polymerization of beaded acrylamide resin is carried out at relatively low temperatures (20-50°C), and the polymerization is complete within a relatively short period (1-5 hr). The polymerization of most acrylamides proceeds at a substantially faster rate than that of styrene in o/w suspension polymerization. The problem with droplet coagulation during the synthesis of beaded polyacrylamide by w/o suspension polymerization is usually less critical than that with a styrene-based resin. 

A closely related asymmetric synthesis of chiral sulphoxides, which involves a direct oxidation of the parent sulphides by t-butylhydroperoxide in the presence of metal catalyst and diethyl tartrate, was also reported by Modena and Di Furia and their coworkers-28-7,288 jjje effect 0f the reaction parameters such as metal catalyst, chiral tartrate and solvent on the optical yield does not follow a simple pattern. Generally, the highest optical purities (up to 88%) were observed when reactions were carried out using Ti(OPr-i)4 as a metal catalyst in 1,2-dichloroethane. 

An example of the efficient formation of an electron-deficient double bond by RCM was disclosed by a Japanese group in a novel total synthesis of the macrosphelides A (209) and B (208) (Scheme 41) [100]. When the PMB-pro-tected compound 204 was examined as a metathesis substrate, the ring closure did not proceed at all in dichloromethane using catalysts A or C. When the reaction was carried out using equimolar amounts of catalyst C in refluxing 1,2-dichloroethane, the cyclized product 205 was obtained in 65% yield after 5 days. On the other hand, the free allylic alcohol 206 reacted smoothly at room temperature leading to the desired macrocycle 207 in improved yield. 

A cyclobutene ROCM sequence was also used in a synthesis of racemic sporochnol (410), a naturally occurring feeding deterrent toward herbivorous fish (Scheme 80) [170]. Exposing cyclobutene 406 (0.01 M in boiling 1,2-dichloroethane) in the presence of ethylene to second-generation catalyst C (8 mol%) led to 1,5-diene 407 in 73% yield, along with 9% of the homodimer derived from 407 by involving the less hindered double bond. Site-selective hy-... 

The synthesis of a PPV derivative, 94, with donor (di-n-hexylamino) and acceptor (nitro) substituents attached regioselectively to the PPV backbone, was published by Yu et al. following the Heck-type cross coupling approach [118] starting from an AB-type monomer (95). The red-orange polymer (94), which is soluble in THE, chloroform and 1,2-dichloroethane, displays a number-average molecular weight M of about 12,000. 

An improved synthesis of 3,4-dihydro-2,l-benzothiazine 2,2-dioxide was reported by Togo and co-workers using photochemical conditions . Treatment of A-alkyl 2-(aryl)ethanesulfonamides 18 with (diacetoxyiodo)arenes under irradiation with a tungsten lamp at 20-30 °C afforded 2,1-benzothiazines 19 and 20. Chemical yields and selectivities were dependent upon the choice of solvents and the reactant s substituents 18 (Table 1). When THF and EtOH were used as solvents, the reactions failed to give the cyclized products, since their a-hydrogen was abstracted by the intermediate sulfonamidyl radical. Compound 20 was obtained as a major product when 1,2-dichloroethane was employed as a solvent. In contrast, in the case of EtOAc as solvent, compound 19 was obtained as the major product. 

In 2001, Sarko and coworkers disclosed the synthesis of an 800-membered solution-phase library of substituted prolines based on multicomponent chemistry (Scheme 6.187) [349]. The process involved microwave irradiation of an a-amino ester with 1.1 equivalents of an aldehyde in 1,2-dichloroethane or N,N-dimethyl-formamide at 180 °C for 2 min. After cooling, 0.8 equivalents of a maleimide dipo-larophile was added to the solution of the imine, and the mixture was subjected to microwave irradiation at 180 °C for a further 5 min. This produced the desired products in good yields and purities, as determined by HPLC, after scavenging excess aldehyde with polymer-supported sulfonylhydrazide resin. Analysis of each compound by LC-MS verified its purity and identity, thus indicating that a high quality library had been produced. 

Almqvist and coworkers have developed a two-step synthesis of optically active 2-pyridones via thiazolines (Scheme 6.216) [388]. Thus, heating a suspension of (R)-cysteine methyl ester hydrochloride with 2 equivalents of an imino ether and 2 equivalents of triethylamine base in 1,2-dichloroethane at 140 °C for 3 min furnished the desired thiazolines in near quantitative yield with limited racemization. Purification by filtration through a short silica gel column and concentration of the filtrate gave a crude product, which was used directly in the next step. Thus, after... 

Recently, a novel method for the synthesis of a library of substituted prolines with microwave technology [95] has been described. In the first step, 1 equivalent of an amine is added to 1.1 equivalents of an aldehyde in 1,2-dichloroethane (DCE), with subsequent irradiation at 180 °C for 2 min. In the second step, 0.85 equivalents of the maleimide are added and the resulting solution is heated at 180 °C for an additional 5 min. This methodology allowed the production of a solution-phase library of 800 compounds with a crude purity between 65 and 82% (Scheme 9.45). The compounds were purified by solid-supported reagent scavenging to afford the final products with a purity between 90 and 98% and in 79-85 % yield [96]. 

As to most chiral atropisomeric ligand, resolution or asymmetric synthesis is requisite. Mikami developed a novel ligand-accelerated catalyst. The chirality of atropos, but achiral triphos ligand-Ru complex, can be controlled by chiral diamines. Using ( -dm-dabn as controller, the single diastereomeric triphos-Ru complex was achieved through isomerization of (i )-triphos-Ru complex in dichloroethane at 80 °G (Scheme l).44... 

A straightforward synthesis for [l,2,4]triazolo[2,3-c][l,3,5]oxadiazinium salts has been described by Hamed et al. <1995JPR274>. The transformation of azaallenium hexachloroantimonate 98 with benzhydrazone was carried out in dichloroethane under reflux conditions to yield the fused quaternary salt 99. 

Fig. 40 Synthesis of a-C-glycosyl derivative of nojirimycin and its analogues. Reagents and conditions (a) BnNH2, PTSA (b) CH2=CHCH2MgBr, Et20 (c) FmocCl, Na2C03 (d) PCC (e) piperidine, DMF (f) NaHB(OAc)3, AcOH, Na2S04, 1,2-dichloroethane, -35 °C.

Although the benzoylformate complex 38a seems to be rather stable an aerobic solution of 38a in 1,2-dichloroethane decomposed within two weeks forming red crystals of the ruthenium(III) complex [Ru(bdmpza)Cl2(PPh3)] (40) (Fig. 30), which were also obtained in a direct synthesis with RuClg x H2O, PPhg and Hbdmpza (44). 

Synthesis of natural-type aminopolysaccharide having dibenzylchitin structure was achieved by the polymerization of a sugar oxazoline monomer, 1 having one hydroxy group at position 4 (Scheme 4) [9]. The polymerization was carried out with an acid catalyst in 1,2-dichloroethane solvent at reflux temperature. All the H-NMR, C-NMR, and IR spectra as well as elemental analysis data of the isolated polysaccharide supported that the polymerization proceeded by the stereoregular glycosylation to give (1 4)-... 

Certain transition metal complexes can serve as templates for the synthesis of chelating NHC ligands. For example, 1-phenylphosphole complexes of pal-ladium(II) are attacked in a Diels-Alder reaction by 1-vinylimidazole. If 1,2-dichloroethane is used as the solvent the imidazole is alkylated in situ and then subjected to a spontaneous carbometallation reaction [Eq. (37)]. 

An alternative method of synthesis consists of preparing (+) 2-aminobutanol (34.1.3) by redncing ethyl ester of L-2-aminobutyric acid hydrochloride with hydrogen nsing simnlta-neonsly Raney nickel and platinum oxide catalysts. This gives pure (+) 2-aminobutanol. Reacting this with 1,2-dichloroethane in the presence of sodium hydroxide gives the desired ethambutol (34.1.4) [16,17]. 

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