233585-50-7

Upstream product

• 623-73-4 diazoacetic acid ethyl ester 
• 169698-49-1 (E)-N-(cyclohexylmethylene)-1,1-diphenylmethanamine 
• 2043-61-0 cyclohexanecarbaldehyde 
• 74603-93-3 N-(cyclohexylmethylene)-1,1-diphenylmethanimine 

Downstream Products

• 855419-42-0 (2R,3R)-ethyl 3-(cyclohexyl)aziridine-2-carboxylate 

Relevant academic research and scientific papers

Probing Catalyst Function – Electronic Modulation of Chiral Polyborate Anionic Catalysts

Boroxinate complexes of VAPOL and VANOL are a chiral anionic platform that can serve as a versatile staging arena for asymmetric catalysis. The structural underpinning of the platform is a chiral polyborate core that covalently links together alcohols (or

Catalytic Asymmetric Aziridination of Benzhydryl Imines and Diazoacetate Esters with BOROX Catalysts from 3,3′-Disubstituted VANOL Ligands

This work details the synthesis of 22 new chiral VANOL ligands that differ by the nature of the substituent in the 3- and 3′-positions of the ligand. These ligands were incorporated into boroxinate catalysts that were used to screen the catalytic asymmetric aziridination of benzhydryl imines with ethyl diazoacetate. Each catalyst was screened in the reaction of imines generated from benzaldehyde and cyclohexanecarboxaldehyde and some with 4-nitro- and 4-methoxybenzaldehyde. In addition, the first report of the effect of the ester substituent of the diazoacetate ester on the asymmetric induction in these aziridination reactions is presented. The first X-ray structure of a boroxinate catalyst generated from a VANOL-derived ligand is also reported.

The iso-VAPOL ligand: Synthesis, solid-state structure and its evaluation as a BOROX catalyst

The new vaulted biaryl ligand iso-VAPOL is an isomer of VAPOL but has the chiral pocket of VANOL. The synthesis of iso-VAPOL involves a cycloaddition/electrocyclization cascade (CAEC) similar to one that is used for VAPOL except that the starting material

Vaulted biaryls in catalysis: A structure-activity relationship guided tour of the immanent domain of the VANOL ligand

The active site in the BOROX catalyst is a chiral polyborate anion (boroxinate) that is assembled in situ from three equivalents of B(OPh) 3 and one of the VANOL ligand by a molecule of substrate. The substrates are bound to the boroxinate by Hbonds to oxygen atoms O1-O3. The effects of introducing substituents at each position of the naphthalene core of the VANOL ligand are systematically investigated in an aziridination reaction. Substituents in the 4,4′- and 8,8′-positions have a negative effect on catalyst performance, whereas, substituents in the 7- and 7′-positions have the biggest impact in a positive direction. VANOL destination: The active site in the BOROX catalyst is a chiral polyborate anion (boroxinate; see figure) that is assembled in situ from three equivalents of B(OPh)3 and one of the VANOL ligand by a molecule of substrate. The effects of introducing substituents at each position of the naphthalene core of the VANOL ligand are systematically investigated in an aziridination reaction. Copyright

Catalytic asymmetric aziridination with borate catalysts derived from VANOL and VAPOL ligands: Scope and mechanistic studies

An extended study of the scope and mechanism of the catalytic asymmetric aziridination of imines with ethyl diazoacetate mediated by catalysts prepared from the VANOL and VAPOL ligands and triphenylborate is described. Nonlinear studies with scalemic VANOL and VAPOL reveal an essentially linear relationship between the optical purity of the ligand and the product suggesting that the catalyst incorporates a single molecule of the ligand. Two species are present in the catalyst prepared from B(OPh)3 and either VANOL or VAPOL as revealed by 1H NMR studies. Mass spectral analysis of the catalyst mixture suggests that one of the species involves one ligand molecule and one boron atom (B1) and the other involves one ligand and two boron atoms (B2). The latter can be formulated as either a linear or cyclic pyroborate and the 11B NMR spectrum is most consistent with the linear pyroborate structure. Several new protocols for catalyst preparation are developed which allow for the generation of mixtures of the B1 and B2 catalysts in ratios that range from 10:1 to 1:20. Studies with catalysts enriched in the B1 and B2 species reveal that the B2 catalyst is the active catalyst in the VAPOL catalyzed asymmetric aziridination reaction giving significantly higher asymmetric inductions and rates than the B1 catalyst. The difference is not as pronounced in the VANOL series. A series of 12 different imines were surveyed with the optimal catalyst preparation procedure with the finding that the asymmetric inductions are in the low to mid 90s for aromatic imines and in the mid 80s to low 90s for aliphatic imines for both VANOL and VAPOL catalysts. Nonetheless, the crystallinity of the N-benzhydryl aziridines is such that nearly all of the 12 aziridine products screened can be brought to >99% ee with a single recrystallization.

An efficient synthesis of (-)-chloramphenicol via asymmetric catalytic aziridination: a comparison of catalysts prepared from triphenylborate and various linear and vaulted biaryls.

[reaction--see text] The antibiotic (-)-choramphenicol has been synthesized in only four steps from p-nitro-benzaldehyde in optically pure form from an asymmetric catalytic aziridination reaction with a chiral catalyst prepared from triphenylborate and the (R)-VAPOL ligand. Catalysts generated from the VAPOL and VANOL ligands give much higher asymmetric induction than do catalysts prepared from 6,6'-diphenylVAPOL, BINOL, and BANOL ligands.

Catalytic asymmetric aziridination with arylborate catalysts derived from VAPOL and VANOL ligands

The asymmetric induction is essentially identical for a range of substrates when the VAPOL and VANOL (see picture; but not 1,1′-binaphth-2-ol (BINOL)) ligands were employed in asymmetric aziridinations catalyzed by triphenylborate (90-98% ee). The synthetic utility of these catalysts is illustrated in a synthesis of L-3,4-dihydroxyphenyl-alanine (L-DOPA).