Enantioselective hydrophosphonylation

Heteroaromatic aldehydes undergo similar enantioselective hydrophosphonylation reactions (Scheme 5-34). 

Groger, H., Saida, Y., Sasai, H., Yamaguchi, K., Martens, J., and Shibasaki, M., A new and highly efficient asymmetric route to cyclic a-amino phosphonates the first catalytic enantioselective hydrophosphonylation of cyclic imines catalyzed by chiral heterobimetallic lanthanoid complexes, /. Am. Chem. Soc., 120, 3089, 1998. 

Jacobsen et al. found that cyclohexane-diamine bifunctional catalyst 216 promoted the enantioselective hydrophosphonylation of A-benzyl imines [110]. Using a modified... 

Akiyama T, Morita H, Itoh J, Fuchibe K (2005a) Chiral Brpnsted acid catalyzed enantioselective hydrophosphonylation of imines asymmetric synthesis of alpha-amino phosphonates. Qrg Lett 7 2583-2585 Akiyama T, Saitoh Y, Morita H, Fuchibe K (2005b) Enantioselective Mannich-type reaction catalyzed by a chiral Bronsted acid derived from TADDOL. Adv Synth Catal 347 1523-1526... 

Catalytic Enantioselective Hydrophosphonylation of Aldehydes. LLB catalyzes the hydrophosphonylations of aldehydes with dimethyl phosphite to afford a-hydroxy phosphonates with high optical purity (eq 7). In some cases, the aldehyde needs to be added slowly to the mixture of LLB and phosphite in THF. For some aromatic aldehydes, another catalyst, Li[Al(binol)2] (ALB), gives better results. Imines also react with dimethyl phosphite in a highly enantioselective manner when potassium-based complexes (K3[Ln(binol)3], LnPB) are used as catalysts. ... 

Thiourea-catalysed enantioselective hydrophosphonylation of imines (370) using phosphite (371) provides a general and convenient route to a wide range of highly enantiomerically enriched a-amino phosphonates (372). The deprotection of these products yields the corresponding a-amino phosphonic acids (373) (Scheme 95). ... 

Heterobimetallic catalysis mediated by LnMB complexes (Structures 2 and 22) represents the first highly efficient asymmetric catalytic approach to both a-hydro and c-amino phosphonates [112], The highly enantioselective hydrophosphonylation of aldehydes [170] and acyclic and cyclic imines [171] has been achieved. The proposed catalytic cycle for the hydrophosphonylation of acyclic imines is shown representatively in Scheme 10. Potassium dimethyl phosphite is initially generated by the deprotonation of dimethyl phosphite with LnPB and immediately coordinates to the rare earth metal center via the oxygen. This adduct then produces with the incoming imine an optically active potassium salt of the a-amino phosphonate, which leads via proton-exchange reaction to an a-amino phosphonate and LnPB. 

Scheme 23. Enantioselective hydrophosphonylation catalyzed by (R)-LnPB complexes.

Scheme 39 Proposed mechanism for enantioselective hydrophosphonylation of enones catalyzed by a dinuclear zinc complex...

The chiral catalyst (352) has been detected by low-temperature NMR and applied in a highly efficient and enantioselective hydrophosphonylation of aldehydes (Scheme 80). ... 

The first catalytic enantioselective hydrophosphonylations of ketimines (363) using commercially available cinchona alkaloids (364) and (365) have been reported by Nakamura et al. (Scheme 83). ... 

Scheme 2.50 Enantioselective hydrophosphonylation to aldimines with the use of chiral heterobimetallic lanthanum(iii) potassium(i) tris(binaphtholate).

An efficient organocatalytic enantioselective hydrophosphonylation of imines to numerous enantiomerically enriched (R)-amino phosphonates was reported by Pettersen and Fini. The enantioselectivity was found to be N-protecting group and solvent depended. Thus, replacing Ts with Boc raised the ee of the product from 48 to 68% and replacing toluene with xylene further increased the ee to an acceptable 80% (for Ar = Ph). Quinidine yielded the opposite enantiomer in considerably lower ee (45%), but unfortunately, unlike quinine (Scheme 15.3), was not tested under optimised conditions and with a representative selection of aromatic imines. 

The first example for catalytic and enantioselective hydrophosphonylation of cyclic imines using cyclic phosphites is the lanthanide BINOL complex catalyzed hydrophosphonylation of 3-thiazolines. The pharmacologically interesting thiazolidinyl phosphonates are synthesized with excellent optical purities of up to 99% ee using the ytterbium-BINOL complex (116). 

For selected pioneering examples, see (a) D. Uraguchi, K. Sorimachi, M. Terada, J. Am. Chem. Soc. 2004, 126, 11804-11805. Organocatalytic asymmetric aza-Friedel-Crafts alkylation of furan. (b) T. Akiyama, H. Morita, J. Itoh, K. Fuchibe, Org. Lett. 2005, 7, 2583-2585. Chiral Br0nsted acid catalyzed enantioselective hydrophosphonylation of imines asymmetric synthesis of a-amino phosphonates. 

One approach is enantioselective hydrophosphonylation. Chiral 1-hydroxyalkylphosphonates M2 could be prepared by the enantioselective hydrophosphonylation of dialkyl phosphonates Ml and aldehydes (Scheme 6.4) [50-54]. 

Scheme 6.4 Asymmetric synthesis of l-hydioxyalkylphosphonates M2 by enantioselective hydrophosphonylation...

In order to obtain 1-hydroxyaIkylphosphonates M2 and cyclic 1-hydrox-yalkylphosphonates IVB in a higher enantiomeric excess (ee), we developed an efficient method [57] to asymmetrically synthesize M2 and IVB via enantioselective hydrophosphonylation of aldehydes using tridentate Schiff base Al(III) complexes as catalysts (Scheme 6.6). 

Merino P, Marques E, Herrera RP et al (2008) Catalytic enantioselective hydrophosphonylation of aldehydes and imines. Adv Synth Catal 350 1195-1208... 

Zhou X, Liu XH, Yang X et al (2008) Highly enantioselective hydrophosphonylation of aldehydes catalyzed by tridentate schiff base aluminum(III) complexes. Angew Chem Int Ed 47 392-394... 

Hydroxyalkylphosphonates M2 were synthesized asynunetrically via enantioselective hydrophosphonylation of aldehydes using tridentate Schi f base A1(III) complexes as catalysts (Scheme 9.31). 

More recentiy, aluminum salalen complex 112 was used by Katsuki et al. for enantioselective hydrophosphonylation of imines." The reaction has a broad scope, giving access to a variety of phosphonic amino acids analogs, and in most cases, products with high ee could be obtained (Scheme 47.26). 

Ito K, Tsutsumi H, Setoyama M, Saito B, Katsuki T. Enantioselective hydrophosphonylation of aldehydes using an aluminum binaphthyl Schiff base complex as a catalyst. Syn-lett 2007 (12) 1960-1962. 

Schlemminger I, Saida Y, Groger H, Maison W, Durot N, Sasai H, Shibasaki M, Martens J. Concept of improved rigid-ityihow to make enantioselective hydrophosphonylation of cyclic imines catalyzed by chiral heterobimetaUic lanthanoid complexes almost perfect. J. Org. Chem. 2000 65 4818-4825. 

Joly GD, Jacobsen EN. Thiourea-catalyzed enantioselective hydrophosphonylation of imines practical access to enantio-merically enriched a-aminophosphonic acids. J. Anu Chem. Soc. 2004 126 4102-4103. 

Akiyama T, Morita H, Itoh J, Fuchibe K. Chiral Brpnsted acid catalyzed enantioselective hydrophosphonylation of imines asymmetric synthesis of a-amino phosphonates. Org. Lett. 2005 7 2583-2585. 

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