The characteristics of (S)-Diphenylprolinol

Previously, we accept apparent that the spiroaminoborate esters 2 (scheme 1), acquired from chiral amino alcohols and ethylene glycol, are admired catalysts for the agee abridgement of prochiral ketones to access non-racemic alcohols in top purity.5 Furthermore, spiroborate 3 acquired from (S)-diphenylprolinol accomplished the best enantioselectivity for a advanced array ketones.5c,d As allotment of our new efforts to access non-spiro analogues of borate 3, we call actuality the synthesis, abreast and assuming of atypical aminoborate esters 1 and 5, (scheme 2). Additionally, the enantioselectivity of these borates in the abridgement of adumbrative ketones was studied.they acclimated the in situ accumulation of the accepted B-methoxy-oxazaborolidine as a simpler and able agreement for the borane abridgement of acetophenone and α-oxoketoxime ethers.6c Also, Masui6a and added groups.7,8a advised the abridgement of alkyl arylketones application as catalyst, the in situ generated oxazaborolidine 4, acquired from (S)-diphenylprolinol and trimethyl borate. Moreover, added accompanying B-alkoxy-oxazaborolidines accept been appropriate as alive catalytic breed in the abridgement of ketones,6b,9 and in the acknowledgment of accession to aldehydes.8c To our knowledge, these oxazaborolidines accept not been abandoned and/or characterized. Interestingly, if we agitated out the acknowledgment of (S)-diphenylprolinol with trimethyl borate in dry diisopropyl ether at allowance temperature, the aminoborate circuitous 1 was acquired as a apparent admixture in 68% yield. The artefact was characterized by 1H, 13C, 11B NMRs and IR spectroscopic analysis.Organocatalytic agee domino sulfa-Michael/aldol abstract reactions amid 1,4-dithiane-2,5-diol (the dimer of mercaptoacetaldehyde) and cinnamaldehydes were calmly answer by (S)-diphenylprolinol TMS ether in the attendance of acerbity acerbic derivatives, arch to ahead alien 4,5-dihydrothiophene-2-carbaldehydes in abstinent to acceptable yields and acceptable enantioselectivities.
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