Chiral bicyclic guanidine

Corey, E. J. Grogan, M. J. Enantioselective Synthesis of a-Amino Nitriles from N-Benzhydryl Imines and HCN with a Chiral Bicyclic Guanidine as Catalyst Org Lett. 1999,1,157-160. 

FIGURE 4. Molecular structure of nitric salt of chiral bicyclic guanidine (13)78. Reproduced by per-mission of the Royal Society of Chemistry... 

Chiral bicyclic guanidine (221) has been identified as an excellent catalyst for reactions between anthrones (219) and various dienophiles, such as (220). The catalyst can tolerate a range of substituents and substitution patterns, making several anthrone derivatives suitable for this reaction. Both Diels-Alder and Michael adducts were obtained in excellent yields, high regioselectivities, and high enantioselectivities (<99% ee). This is the first case of a highly enantioselective base-catalysed anthrone Diels-Alder reaction.263... 

Corey EJ, Grogan MJ (1999) Enantioselective synthesis of alpha-amino nitriles from N-benzhydryl imines and HCN with a chiral bicyclic guanidine as catalyst. Org Lett 1 157-160... 

C2-Symmetrical (or pseudo-symmetrical) chiral bicyclic guanidines are synthesized from amino acid derivatives [21b,22]. The typical synthetic route for a 2,7-disubstimted bicyclic system, (5, 5)-2,7-di(hyroxymethyl)-l,5,7-triazabicyclo[4.4.0]dec-l-ene 9, from asparagine is shown in Scheme 4.6 [22a]. 

Davis, A.P. and Dempsey, K.J. (1995) Synthesis and investigation of a hindered, chiral, bicylic guanidine. Tetrahedron Asymmetry, 6, 2829-2840 Corey, E.J. and Grogan, M.J. (1999) Enantioselective s)mthesis of a-amino nitriles from A-henzhydry 1 imines and HCN with a chiral bicyclic guanidine as catalyst. Organic Letters, 1, 157-160. 

Ye, W., Leaw, D., Goh, S.L.M. eta). (2006) Chiral bicyclic guanidines a concise and efficient aziridine-based synthesis. Tetrahedron Letters, 47, 1007-1010. 

Ye, W., Jiang, Z., Zhao, Y. et a/. (2007) Chiral bicyclic guanidine as a versatile Brdnsted base catalyst for the enantioselective Michael reactions of dithiomalonates and P-keto thioesters. Advanced Synthesis and Catalysis, 349, 2454-2458. 

Davis, A.P. Dempsey, K.J. Synthesis and investigation of a hindered, chiral, bicyclic guanidine. Tetrahedron Asymmetry 1995. 5 (11). 2829-2840. 

In addition, several organocatalysts other than cinchona alkaloid derivatives have been developed very recently. As an example, a chiral bicyclic guanidine was found by Tan et al. to be an excellent catalyst for enantioselective Michael additions of malonates or ethyl benzoylacetates to cyclopentenone or... 

A chiral bicyclic guanidine derivative was employed as an organocatalyst for the sulfa-Miehael addition of thiols to tert- mty 2-phthalimido acrylates by Tan et ah, providing the expected chiral Michael adducts in excellent yields and enantioselectivities of up to 92% ee, as shown in Seheme 1.71. ... 

The enantioselective hydrophosphination of A-arylitaconimides was accomplished in the presence of a chiral bicyclic guanidine (Scheme 14-1) ... 

The chiral bicyclic guanidine 170 acts as a Bronsted base catalyst. The hydroxy group controls diastereo- and enantioselectivities in the direct aldol reaction of 5H-oxazol-4-ones (169) with aldehydes (62). The aldol products (171) are easily converted into amides or esters without loss of enantiopurity thus, this method provides synthetically usefiil a,p-dihydroxycarboxylates bearing a chiral quaternary stereogenic center at the a-carbon atom (Scheme 28.18) [88]. 

Scheme 30.13 Asymmetric hydrocyanation supported by a chiral bicyclic guanidine.

More recently, Tan and coworkers successfully broadened the substrate scope and improved the enantioselectivihes for the Diels-Alder reactions of anthrones by utilizing new chiral bicyclic guanidine 84 as catalyst (Figure 38.3) [35]. Notably,... 

In 2009, Tan and coworkers reported that the chiral bicyclic guanidine (S,S)-20 was able to catalyze the enantioselective isomerization of 3-alkynoates to chiral allenoates in what (formally) constitutes a 1,3-hydrogen sigmatropic rearrangement (Scheme 40.29) [33). The reaction took place in hexane at low temperature with high enantioselectivities, but conversions were not complete. 

Leow D, Lin S, Chittimalla SK, Fu S, Tan CH. Enantioselective protonation catalyzed by a chiral bicyclic guanidine derivative. Angew. Chem. Int. Ed. 2008 47 5641-5645. 

Scheme 3.32 Conjugated addition of thiols to tert-butyl 2-phtha]imidoacrylates catalyzed by chiral bicyclic guanidine...

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