Halides arsinic acids

The esters of arsinic acid are more thermally labile, often resinifying on distillation. However, catalysed pyrolyses using alkyl halides, salts or mineral acids afford useful yields ca 50%) of arsenic(III) esters . The mechanism is considered to involve the pyrolysis of an alkoxyarsonium salt 7 is formed with the catalyst. 

SCHEME 8. The alternative reaction routes of the intermediate alkoxyarsonium salts in the alkyl halide catalysed decomposition of the esters of arsinic acids ... 

Arsinic acids have been prepared by similar methods as for the preparation of arsonic acids. Thus, reaction of sodium organoarsenites with alkyl halides (Meyer reaction) and reaction of sodium organoarsenite with arenediazonium salts (Bart reaction) are available for the preparation of arsinic acids. Several examples are shown in equations 333 and 334. ... 

The pyrolysis of organoarsenic compounds containing the arsenyl moiety has some limited preparative applications [arsenyl (As=0) by analogy with phosphoryl (P=0)]. The compounds are based on the arsonic acid RAs(0)(0H)2, the arsinic acid R2As(0)0H and the arsine oxide R3As=0 structures. The acids are in interesting contrast with the phosphorus series. The phosphonic and phosphinic esters are prepared from the phosphorus(III) precursors via the Arbuzov synthesis. This synthetic route fails with the arsenic analogues, and further, if an alkyl halide or a salt is added in the pyrolysis of arsonic or arsinic acid esters a retro-Arbuzov reaction takes place . ... 

Arsonic and Arsinic Acids. The arsonic acids, compounds of the type RAsO(OH)2, are among the most important organic arsenicals. The aliphatic arsonic acids are generally prepared by the Meyer reaction ie, heating an alkyl halide with As406 in alkaline solution ... 

Where X is Br or Cl, the free acids may be obtained by acidification of the alkaline solution, but where X is I, the acids must be isolated as salts to avoid reduction of the arsonic acids by HI. Rather than using alkyl halides, alkyl or dialkyl sulfates or alkyl arenesulfonates can be used. Primary alkyl halides react rapidly and smoothly, secondary halides react only slowly, whereas tertiary halides do not give arsonic acids. Allyl halides undergo the Meyer reaction, but vinyl halides do not. Substituted alkyl halides can be used eg, ethylene chlorohydrin gives 2-hydroxyethylarsonic acid [65423-87-2], C2H7As04. Arsinic acids, R sC OH), are also readily prepared by substituting an alkali metal arsonite, RAs(OM)2, for sodium arsenite ... 

The arsine analogues of this series, [MoX2(diars)2] (X = Cl, Br, I) have been obtained by the anaerobic reaction of acid molybdenum(III) halide solutions with diars in water and/or alcohol. They are paramagnetic (p.es 2.8-2.9BM), with a possible d-d UV band at 11000 cm-1 in [MoCl2(diars)2].74... 

These are prepared by the cyclization of either an arsenous chloride (29) (23JCS2489) or an arsenic acid (30) (58JCS1719). These routes have been used to prepare both the 1-methyl-and the 1-phenyl-arsindolines. The arsindolines show the normal properties of tertiary arsines and form addition compounds with alkyl halides or palladium dibromide. Attempts to dehydrogenate arsindolines to the parent arsindoles (31) have not been successful (Scheme 7). 

Osmium pentacarbonyl is a convenient precursor to other osmium carbonyl complexes. Hydrogenation gives the dihydride OsH2(CO)4. This hydride is not acidic with a p/fa of 18.5 but it can be deprotonated by strong bases to give [OsH(CO)4] and reduced by sodium (Scheme 23). Substitution of CO on Os(CO)5 by trialkyl or triarylphosphines, arsines, or stibenes gives Os(CO)4L or Os(CO)3L2. Other carbonyl phosphine complexes result from the reduction of osmium halides by alcohols in the presence of the tertiary phosphine. 

The phenyl derivatives of these acids were known as early as 1876, owing to the fact that they are obtainable from halogenated arsines when the latter are treated with water. The older methods for isolating arylarsinic acids consist in decomposing aryl or diarylarsine halides, tetrahalides, or oxyhalides by water ... 

The achiral 14-membered trans-diimine macrocycle (f , S )-102, in the presence of trifluoroacetic acid, rearranges quantitatively into the chiral seven-membered monoimine ( )-103 (Section Ill.C.l.h)". If the rearrangement of (i , S )-102 is carried out in methanol containing a suspension of ( )-(—)-78, an orange solution is obtained from which pure [I ,(Sas,I as)] ( )-1 6 can be isolated by the addition of ammonium hexafluorophosphate. The yield of the complex was ca 50%. The addition of more acid and halide in an attempt to facilitate racemization of the free arsine and thereby promote the further crystallization of the complex by second-order asymmetric transformation was unsuccessful. Nevertheless, this highly stereoselective synthesis of [H,(Sas,IIas)] ( ) 106 is a more expedient route to (R,I )-(—)-102 than the one involving resolution of the benzyl alcohol complex (R, SA.)-(-)-92a. 

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