Cinchona phosphinate

The catalyst is a combination of a chemo-catalyst and a natural product taken from the cinchona alkaloids giving amazing results. In phosphine catalysed asymmetric catalysis these types of structures are lacking, as nature does not produce phosphines ( ) and the phosphines used in the early years of development of asymmetric homogeneous catalysis lacked the complexity of... 

Most of the examples given in the preceding text relied on silver phosphine complexes as catalysts. The. Mrgensen group examined the use of cinchona-derived ligands in the silver fluoride-catalyzed reaction of aromatic iminoesters 103 with methylacrylate (27). Yields were excellent, but enantioselectivities were only in the... 

Using chiral cinchona alkaloid derived PT catalysts (but achiral phosphines ), new amino acid derivatives were obtained in enantiomeric ees up to 96% [92], (3) The unusual coupling of four molecules sketched above was accomplished in high yield with Pd(0)/bis(dibenzylideneacetone) as metal and NBu4Br as PT catalyst in aqueous NaOH/CH2Cl2 at room temperature. 

Chiral base catalysis is one of the most versatile and broadly applicable types of catalysis. In particular, the potential of tertiary amines to act both as a base and as a nucleophilic catalyst makes chiral tertiary amines like Cinchona alkaloids a privileged catalyst structure in modem synthesis chemistry. In addition, the field of achiral phosphine and carbene catalysis has proven its potential in numerous applications in the past and it is probably only a matter of time until chiral phosphines and carbenes will also be used routinely for other presently demanding natural product total synthesis (Table 7). 

In this work, the combination of cinchona-alkaloid-derived primary amine and Au(I) phosphine complex has been employed to effect two consecutive Friedel-Crafts-type reactions of pyrrole in one pot to furnish 2,3-annulated pyrroles containing a seven-membered ring (eq 1) This reaction proceeds through initial asymmetric 1,4-addition of p)rrole to enones catalyzed by the primary amine followed by an intramolecular 7-c/ido-dig cycliza-tion catalyzed by the Au(I) phosphine complex. 

Ye, Liang, and coworkers reported the addition of diphenylphosphine oxide to enones catalyzed by a bifunctional primary amine thiourea catalyst (127) derived from cinchona alkaloid (Scheme 33.38) [119], Cyclic and acyclic enones react with phosphine oxides under the optimized conditions to furnish the phosphine derivatives 128 in excellent yields and enantioselectivities. The primary amine of the catalyst activates the enone via an iminium, while the thiourea moiety activates and directs the phosphine group. 

The proposed reaction mechanism and stereochemical rationale (Figure 3.9) closely mirrors the proposal for the cinchona alkaloid catalyzed homodimerization, in that addition of phosphine 121 anti to the larger substiment of ketene... 

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