1072879-81-2

Upstream product

• 623-73-4 diazoacetic acid ethyl ester 
• 1072879-63-0 N-phenylmethylidene-1,1-bis(4-methoxy-3,5-dimethylphenyl)methylamine 
• 64-17-5 ethanol 
• 100-52-7 benzaldehyde 
• 91-00-9 Benzhydrylamine 
• 1072879-54-9 3,3',5,5'-tetramethyl-4,4'-dimethoxy benzhydrylamine 

Relevant academic research and scientific papers

Isotope effects and mechanism of the asymmetric BOROX br?nsted acid catalyzed aziridination reaction

The mechanism of the chiral VANOL-BOROX Br?nsted acid catalyzed aziridination reaction of imines and ethyldiazoacetate has been studied using a combination of experimental kinetic isotope effects and theoretical calculations. A stepwise mechanism where re

Multicomponent Catalytic Asymmetric Synthesis of trans-Aziridines

A multicomponent trans-aziridination of aldehydes, amines, and diazo compounds with BOROX catalysts is developed. The optimal protocol is slightly different for aryl aldehydes than for aliphatic aldehydes. The key to the success with aryl aldehydes was allowing the catalyst, aldehyde, and amine to react for 20 min before addition of the diazo compound. A variety of 11 different electron-poor and electron-rich aryl aldehydes were screened to give trans-aziridines in 73-90% yield with 82-99% ee and trans/cis selectivities of 19:1 to >99:1. The optimal protocol for the trans-aziridination of aliphatic aldehydes did not require prereaction of the catalyst, aldehyde, and amine, and instead, the diazo compound could be added directly. The scope of the reaction is limited to unbranched aliphatic aldehydes and was tolerant of a number of functional groups including ethers, esters, epoxides, carbamates, and phthalimides. A total of 10 aliphatic aldehydes were examined and found to give trans-aziridines in 60-88% yield with 60-98% ee and trans/cis selectivities of 6:1 to >99:1. Alkenyl aldehydes did not react, but an alkynyl aldehyde gave a 71% yield and 95% ee of an aziridine that was found to be the cis- and not the trans-diastereomer. The aryl and aliphatic aldehydes both gave the trans-aziridines with the same absolute configuration with the same catalyst; however, in those cases where cis-aziridines were formed, the configuration was opposite for those formed from aryl versus aliphatic aldehydes.

Pyro-Borates, Spiro-Borates, and Boroxinates of BINOL - Assembly, Structures, and Reactivity

VANOL and VAPOL ligands are known to react with three equivalents of B(OPh)3 to form a catalytic species that contains a boroxinate core with three boron atoms, and these have proven to be effective catalysts for a number of reactions. However, it was not known whether the closely related BINOL ligand will likewise form a boroxinate species. It had simply been observed that mixtures of BINOL and B(OPh)3 were very poor catalysts compared to the same mixtures with VANOL or VAPOL. Borate esters of BINOL have been investigated as chiral catalysts, and these include meso-borates, spiro-borates, and diborabicyclo-borate esters. Borate esters are often in equilibrium, and their structures can be determined by stoichiometry and/or thermodynamics, especially in the presence of a base. The present study examines the structures of borate esters of BINOL that are produced with different stoichiometric combinations of BINOL with B(OPh)3 in the presence and absence of a base. Depending on conditions, pyro-borates, spiro-borates, and boroxinate species can be generated and their effectiveness in a catalytic asymmetric aziridination was evaluated. The finding is that BINOL borate species are not necessarily inferior catalysts to those of VANOL and VAPOL but that, under the conditions, BINOL forms two different catalytic species (a boroxinate and a spiro-borate) that give opposite asymmetric inductions. However, many BINOL derivatives with substitutents in the 3- and 3′-positions gave only the boroxinate species and the 3,3′-Ph2BINOL ligand gave a boroxinate catalyst that gives excellent inductions in the aziridination reaction. BINOL derivatives with larger groups in the 3,3′-position will not form either spiro-borates or boroxinate species and thus are not effective catalysts at all.

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

A general synthesis of sphinganines through multicomponent catalytic asymmetric aziridination

A catalytic asymmetric synthesis of all four stereoisomers of sphinganine is described starting from hexadecanal. Utilizing either the (R) or (S) enantiomer of a BOROX catalyst, a multicomponent reaction of this aldehyde with an amine and ethyl diazoacetate gives rise to enantiomeric aziridine-2- carboxylates. Access to all diastereomers of sphinganine is realized upon ring opening of the enantiopure aziridine-2-carboxylate at the C-3 position by direct SN2 attack of an oxygen nucleophile, which occurs with inversion of configuration and by ring expansion of an N-acyl aziridine to an oxazolidinone and then hydrolysis. Overall, this process results in the formal ring opening of the aziridine with an oxygen nucleophile with retention of configuration. The synthesis of all four stereoisomers of sphinganine was achieved by multi-component asymmetric aziridination of hexadecanal. Complete stereocontrol is realized with the proper choice of the chirality of the BOROX catalyst and the introduction of an oxygen substituent at the 3-position of the aziridine with either retention or inversion. MEDAM = tetramethyldianisylmethyl. Copyright

A General Synthesis of Sphinganines through Multicomponent Catalytic Asymmetric Aziridination

A catalytic asymmetric synthesis of all four stereoisomers of sphinganine is described starting from hexadecanal. Utilizing either the (R) or (S) enantiomer of a BOROX catalyst, a multicomponent reaction of this aldehyde with an amine and ethyl diazoacetate gives rise to enantiomeric aziridine-2-carboxylates. Access to all diastereomers of sphinganine is realized upon ring opening of the enantiopure aziridine-2-carboxylate at the C-3 position by direct SN2 attack of an oxygen nucleophile, which occurs with inversion of configuration and by ring expansion of an N-acyl aziridine to an oxazolidinone and then hydrolysis. Overall, this process results in the formal ring opening of the aziridine with an oxygen nucleophile with retention of configuration.

BOROX catalysis: Self-assembled AMINO-BOROX and IMINO-BOROX chiral Bronsted acids in a five component catalyst assembly/ catalytic asymmetric aziridination

A five-component catalyst assembly/aziridination reaction is described starting from an aldehyde, an amine, ethyl diazoacetate, B(OPh)3, and a molecule of a vaulted biaryl ligand (VAPOL or VANOL). A remarkable level of chemoselectivity was observed since, while 10 different products could have resulted from various reactions between the five components, an aziridine was formed in 85% yield and 98% ee and only two other products could be detected in 3% yield. Studies reveal that the first in a sequence of three reactions is an exceedingly rapid amine-induced assembly of an AMINOBOROX chiral Bronsted acid species from VAPOL and B(OPh)3, which is followed by imine formation from the amine and aldehyde and the concomitant formation of an IMINO-BOROX chiral Bronsted acid and finally the reaction of the imine with ethyl diazoacetate mediated by the IMINO-BOROX catalyst to give aziridine-2-carboxylic esters with very high diastereo- and enantioselectivity.

Seeking passe-partout in the catalytic asymmetric aziridination of imines: Evolving toward substrate generality for a single chemzyme

The asymmetric catalytic aziridination reaction (AZ reaction) of imines derived from dianisylmethyl (DAM) amine and tetra-methyldianisylmethyl (MEDAM) amine were examined with boroxinate catalysts prepared from both the VANOL and VAPOL ligands. This included an evaluation of different protocols for the preparation of the catalyst. The AZ reaction of DAM and MEDAM imines prepared from nine different aryl and aliphatic aldehydes were examined. The MEDAM imines were superior to the DAM imines in the AZ reaction, giving much higher asymmetric inductions and higher overall yields of aziridines. The MEDAM imines were found to also be superior to the previously studied diphenylmethyl (benzhydryl or Bh) and tetra-tert-butyldianisylmethyl (BUDAM) imines especially for imines derived from aliphatic aldehydes. The average asymmetric induction over the nine different MEDAM imines studied was 97% ee with the VAPOL catalyst and 96% ee with the VANOL catalyst. The MEDAM imines can be deprotected to give N-H aziridines in all cases except for some electron-rich aryl aldehydes. The MEDAM imines are much more reactive than benzhydryl imines, and this was most evident when a diazoacetate ester is replaced by a diazoacetamide. The less reactive diazoacetamides give very low yields in their reactions with benzhydryl imines but high yields with MEDAM imines.

Mapping the active site in a chemzyme: Diversity in the N-substituent in the catalytic asymmetric aziridination of imines

(Chemical Equation Presented) The active site of the aziridination catalyst derived from either the VANOL or VAPOL ligand and B(OPh)3 is larger than expected and can accommodate not only significant substitution on the diarylmethyl unit of the imine but also that alkyl (but not perfluorylalkyl) substituents on the aryl groups lead to enhanced rates and enantioselection. The screen of diarylmethyl N-substituents on the imine revealed that the 3,5-di-tert-butyldianisylmethyl group (BUDAM) gave exceptionally high asymmetric inductions for imines of aryl aldehydes.