Proline catalysts phosphine

Proline-derived phosphines (254) produced efficient catalysts in situ with [Ir(cod)]2BArp for the asymmetric hydrogenation of olefins in CH2CI2. These ligands gave high enantioselectivities with several classes of alkenes, most notably a,p unsaturated carboxylic esters and ketones. ... 

Excellent stereoselectivities (<99 1 dr and <99% ee) have been attained for the Michael addition of ketones to nitroalkenes, catalysed by the polyfunctional secondary-secondary-tertiary triamines (216) and (217). ° The proline-derived phosphine oxide (218) also exhibited a high level of stereocontrol (<99 1 dr (syn/anti) and <96% Catalyst (219) has been designed computationally for... 

The development of chiral peptide-based metal catalysts has also been studied. The group of Gilbertson has synthesized several phosphine-modified amino adds and incorporated two of them into short peptide sequences.[45J,71 They demonstrated the formation of several metal complexes, in particular Rh complexes, and reported their structure as well as their ability to catalyze enantioselectively certain hydrogenation reactions.[481 While the enantioselectivities observed are modest so far, optimization through combinatorial synthesis will probably lead to useful catalysts. The synthesis of the sulfide protected form of both Fmoc- and Boc-dicyclohexylphosphinoserine 49 and -diphenylphosphinoserine 50 has been reported, in addition to diphenylphosphino-L-proline 51 (Scheme 14).[49 To show their compatibility with solid-phase peptide synthesis, they were incorporated into hydrophobic peptides, such as dodecapeptide 53, using the standard Fmoc protocol (Scheme 15).[451 For better results, the phosphine-modified amino acid 50 was coupled as a Fmoc-protected dipeptide 56, rather than the usual Fmoc derivative 52.[471 As an illustrative example, the synthesis of diphe-nylphosphinoserine 52 is depicted in Scheme 16J45 ... 

Using a chiral auxiliary via an amide or ester leads to asymmetric induction. Aryl aldehydes and conjugated ketones were condensed using proline, leading to modest enantioselectivity. °° Chiral biaryl catalysts have been used with trialkyl-phosphines, giving good enantioselectivity. ° Chiral quinuclidine catalysts lead to... 

Michael reaction. Different ligands for copper catalysts are available. For example, an oxazoline prepared from valine," a phosphine from proline,"" and a carbohydrate-based thiolhave been tested. 

A commercially available and inexpensive proline- or pipecoline acid-promoted copper-catalyst system has been developed for the preparation of arylphosphonates, arylphosphinates and aryl phosphine oxides (136) through P-arylation of //-phos-phonates (137) (Scheme 48). ... 

The Heck reaction (also called the Mizoroki-Heck reaction) is the chemical reaction of an unsaturated halide with an alkene in the presence of a base and a palladium catalyst (or palladium nanomateiial-based catalyst) to form a substituted alkene. An efficient and simple protocol for phosphine-free Heck reactions in water in the presence of a Pd(L-proline)2 complex as the catalyst under controlled micro-wave irradiation conditions is versatile and provides excellent yields of products in short reaction times (Scheme 8.17) [20], The reaction system minimizes costs, operational hazards, and envirorunental pollution. 

Allam BK, Singh KN (2011) An elEcient phosphine-free heck reaction in water using Pd(L-Proline)2 as the catalyst under microwave irradiation. Synthesis 2011(7) 1125-1131... 

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