Phase-Transfer Catalyzed Addition of Anion Supplied as Metal Salt

Phase-Transfer-Catalyzed Addition of Anion Supplied as Metal Salt 

The reaction conditions are rather mild, so that the possibility of side reactions, such as catalyst decomposition, is considerably reduced. The major challenge associated with these reactions is an absence of prochirality in the anionic species. Namely, the chiral onium anion must discriminate the enantiotopic face of the distant electronically neutral reaction partner in the organic phase. 

Asymmetric phase-transfer catalyzed oxidation of olefin using sodium hypochlorite or potassium permanganate as metal anion sources is the typical example of this category. 

Starks Extraction Mechanism Brandstrom-Montanari Modification 

With regards to the mechanism of the generation of onium anion, the Starks extraction mechanism and interfacial mechanism (Brandstrom-Montanari modification) are suggested [1-3]. As in the above-described case, the interfadal mechanism seems to be operative in the asymmetric phase-transfer catalysis. 

Phase-transfer-catalyzed asymmetric cyanations [22] with potassium cyanide are also typical examples that fall into this category. 

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