N-Benzylcinchonidinium chloride

Practical synthesis of chiral 9,9'-spirobixanthene-1,1'-diol.[Pubmed:17268642]

Org Biomol Chem. 2006 Dec 21;4(24):4474-7.

A concise four-step synthesis of 9,9'-spirobixanthene-1,1'-diol is reported, featuring a practical preparation at large scale without the use of column chromatography purification. Co-crystallization with N-Benzylcinchonidinium chloride and N-benzylquininium chloride rendered the optically pure product in both enantiomers.

2,8'-disubstituted-1,1'-binaphthyls: a new pattern in chiral ligands.[Pubmed:12561104]

Chemistry. 2002 Oct 18;8(20):4633-48.

The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-Benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product).

Copper(II)-mediated oxidative coupling of 2-aminonaphthalene homologues. Competition between the straight dimerization and the formation of carbazoles.[Pubmed:11312967]

J Org Chem. 2001 Feb 23;66(4):1359-65.

Whereas the Cu(II)-mediated oxidative coupling of 2-aminonaphthalenes 7a and 7b results in the clean formation of 1,1'-binaphthyls 13a and 13b, respectively, their higher homologues and congeners 8-12 have been found to exhibit a different reaction pattern. Thus, 2-aminoanthracene (8) gave a approximately 1:1 mixture of the expected bianthryl derivative 15 and the carbazole 16, whereas the 9-aminophenanthrene (10), 3-phenyl-1-aminonaphthalene (11), and 2-aminochrysene (12) produced almost exclusively the corresponding carbazoles 19, 20, and 21, respectively. By contrast, the isomeric 3-aminophenanthrene (9) gave rise to the azo compound 17 as a result of the preferential oxidation on the nitrogen. The carbazoles have been shown to arise directly from the coupling reactions rather than from the primarily formed binaphthyls. Alternatively, carbazole 19 can also be prepared from 1b on reaction with hydrazine. On the other hand, treatment of 3a with hydrazine resulted in the formation of a approximately 2:7 mixture of amine 11 and arylhydrazine 22. 2,2'-Diamino-1,1'-bianthryl (15) has been resolved into enantiomers via cocrystallization with (-)-N-Benzylcinchonidinium chloride and shown to have (R)-(-)-15 configuration by X-ray crystallography.