Spiro-phosphoramidite

An iridium catalyst containing a spiro phosphoramidite ligand has recently been... 

Hoffman and Carreira [31] reported a Rh-catalyzed asymmetric intramolecular hydroacylation of pent-4-enal substrates, providing P-substituted cyclopentanones in good yield and excellent selectivity by using chiral spiro phosphoramidite-alkene ligand (R)-29 (Scheme 29). 

In 2005, the Zhou group applied the biindane-derived ehiral spiro phosphoramidite and phosphite ligands in the Pd-catalyzed asymmetric hydrovinylation of styrene. However, only moderate yield and enantiose-lectivity could be obtained. Recently, Muller and co-workers synthesized Cj-symmetric tris-binaphthyl monophosphite ligand L29, and used it in the Pd-catalyzed asymmetric hydrovinylation reaction. The hydrovinylation product of styrene could be obtained in 70% conversion and 92% ee (Scheme 9.12). ... 

In addition, Zhou et al have developed diastereo- and enantioselective reductive coupling of 1,3-dienes, such as l,4-diphenylbuta-l,3-diene, with aromatic and heteroaromatic aldehydes by using ZnEt2 as the reducing agent and nickel complexes of chiral spiro phosphoramidites such as 21 (Scheme 4.21). In this case, the three-component reaction provided the... 

The asymmetric hydrovinylation of functionalised alkenes remained a challenge until the work reported by Zhou et aL in 2010, in which chiral spiro phosphoramidite Sa,Rfi)-7 previously reported by these authors was applied to the asymmetric hydrovinylation of silyl-protected allylic alcohols. A range... 

Scheme 5.10 Hydrovinylation of silyl-protected allylic alcohols with an in situ generated nickel catalyst from a spiro phosphoramidite ligand.

Wu S, Zhang W, Zhang Z, Zhang X. Synthesis of new monodentate spiro phosphoramidite ligand and its application in... 

Fu Y, Guo XX, Zhu SF, Hu AG, Xie JH, Zhou QL. Rhodium-catalyzed asymmetric hydrogenation of functionalized olefins using monodentate spiro phosphoramidite ligands. J. Org. Chem. 2004 69(14) 4648 655. 

Zhou et al. have reported extensively on the use of a spiro-biindanediol as the backbone in the ligands 35a-f (Scheme 28.11, SIPHOS) [70]. Excellent results are obtained for a variety of substrates, and recently a full report has appeared on the use of these ligands [71]. Synthesis of the diol backbone requires a number of steps, including a resolution [72]. An additional and successful spiro-diol-derived phosphoramidite 39 has recently been disclosed by the group of Zhang [73]. 

Several spiro-ketal-based phosphoramidites have been prepared by the same research group in multistep sequences (Figure 2.37) [18]. In the hydroformylation of terminal olefins, turnover numbers of up to 2.3 X10 and Ub ratios of 174.4 were stated. 

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