Arsines macrocyclic

Kyba and co-workers employ multistep synthesis and a high dilution technique88,89 for the final cyclization stage (Scheme 2). By variation of the reactants of the final high dilution stage, various novel macrocycles, e.g. [14]aneP2S2 (10), have been synthesized in yields of 30-60%. Kyba also modified this route to produce an 11-membered series of macrocycles (Scheme 3).90 Kyba et al. have used similar techniques to produce a range of arsine macrocycles. 

Earlier relevant reviews on phosphine and arsine macrocycles are given by Stelzer and Langhans2 and Wild.3 There are no examples of stibine or bismuthine macrocycles. 

As for phosphine macrocycles, arsine macrocycles involve very difficult synthetic chemistry. The reasons for the difficulties are essentially threefold (i) the volatility and well-known toxicity of the arsenic-containing precursors (ii) the instability of coordinated As—II functions, which renders template cyclizations of limited use for arsenic macrocycles (iii) the high energy barrier to inversion at arsenic (167.4kJmol 1),41 which means that high-dilution cyclizations of polydentate arsine macrocycles leads to mixtures of stereoisomers which are not at all trivial to separate. On the other hand, the macrocyclic (tertiary) arsines are less susceptible to oxidation than their phosphine analogs. 

There have been surprisingly few developments in the synthesis of arsine macrocycles since the early work of Kyba and co-workers and Kaufmann and Ennen, described in CCC (1987)4 No new macrocycles involving only arsine functions have been reported. However, Wild and co-workers have described the highly stereoselective syntheses of new mixed As2S2- and As2N2-donor... 

Most of the nickel(l) complexes are four-coordinate, either tetrahedral (phosphine and arsine complexes) or square planar (macrocyclic and dithiolene complexes), but five-coordinate complexes are also easily formed in the presence of tetradentate tripodal ligands. 

The reactions of dihydrobilin (1,19-dideoxybiladiene-a, c) with transition metals are strongly influenced by the nature of the metal ion. Thus with Mn(OAc)3 or FeClj the corresponding metallocorrolates have been obtained in high yield, in the presence of chromium or ruthenium salts the reaction product isolated has been the metal free macrocycle, while coordination of rhodium requires the presence of an axial ligand such as a phosphine, arsine or amine [21]. Neutral pentacoordinated rhodium complexes have thus been obtained. Although analysis of the electronic spectra of the reaction mixtures demonstrated that cyclization of the open-chain precursor and formation of metallocorrolates occur even in the absence of extra ligands, no axially unsubstituted rhodium derivative has been reported. 

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. 

The highly functionalized arsine 89 was resolved by the fractional crystallization of the diastereomers (/ ,/ as)-( + )- and (R,Sas)-(—)-92a . Oxidation of the dia-stereomer with BaMn04 produced the corresponding aldehyde complex that was converted into a complex of an optically active trans-As2N2 macrocycle (see below). 

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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