Tris dimethylamino arsine

Tris(dimethyIamino)arsine is prepared by dimethylaminolysis of arsenic(III) chloride in a suitable solvent. The reaction is generally applicable since arsenic(III) iodide and alkyl-haloarsines of the general formula R AsX3 (ra = 1 or 2, X = Cl, Br, or I) have been reported to react similarly with secondary amines. In addition to dimethylamine, other secondary amines, such as diethylamine, have been used to prepare the corresponding tris(dialkylamino)arsine. Tris(dialkyl-amino) arsines have also been prepared by transamination of tris(dimethylamino) arsine with higher-boiling secondary amines such as diethylamine, di-n-butylamine, or piperidine. 

A mixture of 453 g. (2.5 mols) of freshly distilled arsenic (III) chloride and 4 1. of n-hexane is placed in a 5-1. four-necked flask 

The reaction is complete when the clear supernatant solution in the reaction vessel no longer contains chlorine as detected by the addition of dilute nitric acid and silver nitrate solution to ca. 1-ml. of the clear solution withdrawn from the reaction flask. After the reaction is complete, the ice bath is removed, and stirring is continued for 2 hours at room temperature. After standing overnight, the dimethylammonium chloride is filtered and washed with n-hexane, with careful exclusion of the moisture of the atmosphere. The combined filtrates are distilled at atmospheric pressure to remove the solvent. The tris(dimethylamino)arsine distills at 36°/2 mm. (55 to 57°/10 mm.). The yield is 402 g. (78%). 

Tris(dimethylamino)arsine (d2o 1.1248 n 1.4848) is a colorless liquid which is readily hydrolyzed to form arsenic (III) oxide and dimethylamine when brought into contact with water. The compound is soluble in ethers and hydrocarbons. The product is at least 99.5% pure (with respect to hydrogen-containing impurities) as evidenced by the single sharp peak at —2.533 p.p.m. (relative to tetramethylsilane) seen in the proton nuclear magnetic resonance spectrum of the neat liquid. 

Submitted by KURT NIEDENZU and JOHN W. DAWSON Checked by CONSTANCE M. WRIGHTf 

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Both von Hirsch 1U) and Weingarten and White 39) have reported the amination of aldehydes and ketones by tris(dimethylamino)arsine (142) to yield the corresponding gem diamine (143) or enamine (144). Von Hirsch s... 

A reagent more reactive than tris(dimethylamino)arsine employed by Weingarten and White 39) was tetrakis(dimethylamino)titanium (145). With this compound it was possible to prepare N,N-dimethyl(l-isopropyl-2-methylpropcnyl)amine (147) from diisopropyl ketone. Weingarten and White 39) have suggested a possible mechanism for this reaction (see p. 88). If benzaldehyde 39,111), formaldehyde 111), or acetaldehyde 39) is used, the corresponding gem diamine or aminal (143) is formed. 

Analogous to 1,2,3-benzazadiphospholes (Section 4.22.10) 1,3,2-benzazaphosphaarsole (39) and 1,3,2-benzazaphosphastibole (37) results from the condensation of 2-aminophenylphosphine (38) and tris(dimethylamino)arsine or stibine (Scheme 9) <93PS(76)45>. 

Reaction of tris(dimethylamino)arsine or tetrakis(dimethylamino)-titanium with aldehydes or ketones to give enamines [164, 165]. 

The As—N bond is labile and this has been widely exploited in synthetic arsenic chemistry. Some idea of the versatility168 can be seen from Schemes 1 and 2. Refluxing secondary amines with tris(dimethylamino)arsine effects transamination (equation 6). These tris(dialkyl-amino)arsines undergo the general reactions in Scheme 1, enabling ready access to a wide variety of compounds, many of them finding use as ligands in transition metal complexes (see Chapter 14 of this work). 

Grignard reagents are not enough basic to abstract a vinylic hydrogen, nor do they participate in halogen metal exchange. As shown, they instead substitute the reactive chlorine atom in a-chloroenamines. More recent work has shown that 87 a, R = Me can be obtained from co-chloroacetophenone and tris-dimethylamino) arsine in 86 % yield I61). 

Treatment of 1 -methyl-4-piperidone with tris(dimethylamino)arsine gave an enamine, viz., l-methyl-4-dimethylamino-3-piperideine (12).11... 

Reaction of pyrylium salts 50f and 7 with tris(dimethylamino)phosphine 223 (Scheme 43) affords the phosphonium adducts 224a-b, whereas treatment of 7 with tris(dimethylamino)arsines 225 and the stibine homolog 226 leads a new series of pentamethinium salts, e.g., 227 (92TL1741). 

Elements of Group V Bonds to Oxygen.—Alcohol groups can be displaced from triethoxyarsine by oximes or diethylhydroxylamine in a stepwise manner to give the products (EtO)3-nAs(ON=CR1R2) .659 Two hew 1,3,2-dioxa-arsolans (92) result when tris(dimethylamino)arsine and either ethylene glycol or pinacol react, and further reaction of these compounds with a -hydroxy-acids leads... 

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