Arsenic ylides synthesis

The thermodynamic data presented in Table XYI are calculated for the temperature T=0K. Note that the entropy factor favors betaine decomposition via directions A and B at higher temperatures. The reactions of organoelement analogs of carbenes with phosphorus and arsenic ylides are yet poorly studied. The presented above results of calculations allow an optimistic prognosis about the possibility of developing a new method for the synthesis of elementaolefins R2E14=CH2 (E14 = Si, Ge, Sn) on the basis of these reactions. 

Reactions of Phosphonic and Arsenic Ylides with Electron Deficient Alkynes and Synthesis of Polyfunctional Fluoroorganics ... 

Decomposition with the elimination of arsenic or phosphorus ylide and formation of silylene (germylene, stannylene) Me2E14, which represents the process inverse to the synthesis of these betaines. 

Chiral arsonium ylides containing the benzylidene group react with aromatic aldehydes to produce trans-2,3-diaryloxiranes with optical purities of up to 41%. The degree of asymmetric induction depends upon the nature of the substituents on the ylide, the substrate, and upon the reaction conditions. For the variety of arsonium ylides investigated, however, the yields of recovered optically active arsines were almost quantitative with complete retention of configuration at arsenic in each case. Thus, apart from the value of stereoselective benzylidene transfer for the asymmetric synthesis of trans-2,3-diaryl oxiranes, the reaction provides the cleanest route to the recovery of optically active arsines from resolved benzylarsonium salts (see Section III.B.5). The mechanism of the reaction, which must take into account the exclusive formation of trans-diaryloxiranes, is believed to occur via the stereoselective decomposition of a pair of (R, S )-betaines (Scheme 16). 

Arsenic, Antimony, and Bismuth.- (Diphenylarsino)methyl-lithium (203) has been prepared by either halogen-lithium or tin-lithium exchange from (204) or (205) respectively. Interestingly the reactivity of (203) depends on the method of preparation used, although the reasons for this are not known. A stereoselective synthesis of JE-a, -unsaturated aldehydes has been achieved by reacting aldehydes with the arsonium salt (206) in the presence of a weak base. The ylide derived from (206) shows a reasonable... 

Arsenic and Bismuth.—A partial asymmetric synthesis of diaryloxirans is dependent on optically active arsonium ylides (89). Yields are high, but optical... 

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