259212-61-8Relevant articles and documents
Synergistic effects within a C2-symmetric organocatalyst: The potential formation of a chiral catalytic pocket
Delaney, Joshua P.,Brozinski, Hannah L.,Henderson, Luke C.
, p. 2951 - 2960 (2013/07/26)
This study describes the synthesis of five novel C2-symmetric organocatalysts that facilitate the on-water asymmetric aldol reaction at low catalyst loading (1 mol%) without the use of additives. Each catalyst is composed of two diprolinamide units joined by a symmetric alkyl bridging group allowing for systematic modulation of catalytic site proximity. Typically, catalysts in this manuscript which bear the catalytic units in close proximity gave the best reaction outcomes in terms of conversion (up to >99%), diastereomeric ratio (4/96, syn/anti) and enantiomeric excess (up to 97%). This effect has been attributed to the assembly of a chiral pocket, facilitated by hydrogen bonding at the oil-in-water interface. The Royal Society of Chemistry 2013.
Thiourea/proline derivative-catalyzed synthesis of tetrahydrofuran derivatives: A mechanistic view
Opalka, Suzanne M.,Steinbacher, Jeremy L.,Lambiris, Brandon A.,McQuade, D. Tyler
experimental part, p. 6503 - 6517 (2011/10/02)
A thiourea/proline derivative-catalyzed synthesis of linear α-substituted tetrahydrofuran/pyran derivatives starting with lactol substrates is presented. This study demonstrates the utility and potential complications of using (thio)urea/proline cocatalysis as each of these catalysts is necessary to provide the observed reactivity, but a time-dependent decrease in enantioselectivity is observed. New mechanistic insights into (thio)urea/proline cocatalysis are presented.
Regioselective synthesis of nitrones by decarboxylative oxidation of N- alkyl-α-amino acids and application to the synthesis of 1-azabicyclic alkaloids
Ohtake, Hiroaki,Imada, Yasushi,Murahashi, Shun-Ichi
, p. 2737 - 2754 (2007/10/03)
Tungstate-catalyzed oxidation of N-alkyl-2a-amino acids with 30% H2O2 solution under phase-transfer conditions gives nitrones regioselectively in good yields: Using this method, stereodivergent synthesis of (R)- and (S)-4- (t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-17a and (S)-17a) was achieved. In addition, (R)- and (S)-3-(t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-45 and (S)-45) were prepared by catalytic oxidation of the corresponding chiral pyrrolidines in a regioselective manner. These chiral cyclic nitrones, 17 and 45 are versatile intermediates for the synthesis of optically active nitrogen heterocycles, since stereoselective additions of carbon nucleophiles to these chiral nitrones can be readily performed. Typically, ZnI2-mediated addition of ketene t-butyldimethylsilyi methyl acetal (29a): to (R)-17a gave the' cis-adduct, methyl (2R,4R)-[1,4-bis(t- butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (cis-30). In contrast, the addition of lithium acetylides 34 to the nitrone (R)-17a gave the trans- adducts, (2S,4R)-2-(1-alkynyl)-4-(t-butyldimethylsilyloxy)-1- hydroxypyrrolidines trans-35. These adducts are useful intermediates for syntheses of the nitrogen heterocycles (3R,5R)-1-aza-3- hydroxybicyclo[3.3.0]octane (37) and (6R,8R)-1-aza-8- hydroxybicyclo[4.30]nonane (38), respectively. The ZnI2-mediated addition of ketene silyl acetal 29a to the nitrone (R)-45 gave methyl (2S, 3R)-[1,3- bis(t-butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (trans-50a), which was used for asymmetric synthesis of the Geissman-Waiss lactone ((-)-49).
