Arsinic acids synthesis

The synthesis of the first arsabenzene, 9-arsaanthracene, 6, was simultaneously communicated by Bickelhaupt16) and Jutzi17> in 1969. The elimination of hydrogen chloride from 9,10-dihydroaarsanthracene 7 afforded 6. These precursors are available from either reduction of the corresponding arsinic acids 816,18) or by the exchange reaction of dihydrostannaanthracenes 9 with arsenic trihalides 17). 

Arsinic acids and arsine oxides may be prepared by extensions of the t Bart synthesis. Thus, diphenylardnic acid is obtained from benzene- diazonium chloride and disodium phenylarsenite. 

For instance in the synthesis of dimethyl arsinic acid (cacodylic acid) trivalent arsenic is isomerised to the pentavalent state... 

The discoverj( of the stereoselective biomethylation of a prochiral arsinic acid by a microorganism opens up an exdting new route to optically active tertiary arsines. Numerous microorganisms reductively methylate arsenic(V) compounds . The biological synthesis of (+)-126 by Scopulariopsis brevicaulis was described in 1936. At that time, however, it was not recognized that simple tertiary arsines chiral at arsenic were configurationally stable and amenable to optical resolution. 

Similarly, the reaction of benzenediazonium chloride with sodium diphen-ylarsenite, (C6Hs)2AsONa, leads to triphenylarsine oxide, (CeHs)3AsO. Arsinic acids are obtained also as by-products in the Bechamp synthesis. For example, 4,4 -diaminodiphenylarsinic acid, along with a... 

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 . ... 

The synthesis of 6-thio- and 6-seleno-a-D-glucopyranose esters of dimethyl-arsinous acid is referred to in Chapter 11 (see Scheme 49). Related 1- and 6-thio- and 1- and 6-seleno-D-glucopyranose esters of dialkyl-phosphinous and -antimonous acids have also been prepared (see also Vol. 9, p. 80). 

Several methods are available for the synthesis of cycloarsoxanes (a) hydrolysis of organoarsenic(III) dihalides RASX2 (X = Cl, Br, I), (b) reduction of arsonic acids RAsO(OH)2 and (c) oxidation of primary arsines RASH2 or cyclopolyarsines (RAs) . The tetramer cyclo-(MeAsO)4 exhibits the boat-chair conformation, whereas the mesityl derivative cyclo-(MesAsO)4 adopts the crown conformation (Figure 11.24). The As-O bond distances are in the range 1.77-1.82 A, typical for single bonds. 

During the decade 1996-2005, in this category of heterocycles, the major interest has been the synthesis and reactions of benzarsepins, arsocanes, and cyclic esters of arsenic(m) acids. In contrast, little work has been done in the area of arsine heteromacrocycles with two or more arsenic atoms. Readers are referred to the corresponding sections of CHEC-II(1996) <1996CHEC-II(9)971 > for information concerning earlier works on macrocyclic polyftertiary arsines) and related compounds. 

In tins synthesis of phenylarsinophenyl-o-arsinie acid, the starting material is o-nitroaniline, whieh, when diazotiscd and coupled with phenyldichloroarsinc, gives o-nitrodiphcnylarsinie acid. Reduction of the latter gives the amino-acid, whieh is (liazotised and the arsinic residue introduced in the usual way. 

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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