Oxazaborolidines as Functional Monomers:  Ketone Reduction Using Polymer-Supported Corey, Bakshi, and Shibata Catalysts

Price, Michael D.; Sui, Jennifer K.; Kurth, Mark J.; Schore, Neil E.

doi:10.1021/jo026132n

Cited by 41 publications

(9 citation statements)

References 12 publications

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“…The oxamides 3 have ideal molecular structures to obtain polycyclic compounds (Scheme 2). Compounds 3 have four coordinating centers that make possible to obtain bis-(1,3,2-oxazaborolidines) by addition of BH 3 -THF. Thus, in this work, we report the synthesis of tricyclic 2,2 -oxy-bis-(1,3,2-oxazaborolidines) 4 by addition of water to bis-(1,3,2-oxazoborolidines) on SCHEME 1 Synthesis of 2,2 -oxy-bis-(1,3,2-oxazaborolidines).…”

Section: Introductionmentioning

confidence: 99%

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New 3,3′[2,2′-oxy-bis-(oxazaborolidine)]-ethylenes. Structural studies by NMR, X-ray, and quantum chemistry methods

et al. 2005

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Section: Introductionmentioning

confidence: 99%

“…

ABSTRACT: 3,3,]ethylene (4a) and 3,3 -[2, 2 -oxy-(4S-methyl-5R-phenyl-1,3,2-oxazaborolidine)-(1,3,2-benzoxazaborolidine)

]ethylene (4b) were synthesized by the reaction of N,N -bis-[(1R,2S)-norephedrine]oxalyl (3a) or N,N -[((1R,2S)-norephedrine

…”

mentioning

confidence: 99%

New 3,3′[2,2′-oxy-bis-(oxazaborolidine)]-ethylenes. Structural studies by NMR, X-ray, and quantum chemistry methods

et al. 2005

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“…Polymer-supported chiral ligand 10 was prepared according to a literature method. 25) cis-1,3-Dibenzyl-tetrahydro-2H-furo[3,4-d]imidazole-2,4,6-trione (3) A mixture of 2 (17.7 g, 50 mmol), acetic anhydride (0.94 ml, 0.01 mol), and xylene (100 ml) was stirred under reflux for 13 h and fixed with a DeanStark apparatus. The solid precipitate was cooled to r.t., filtered and washed with H 2 O (100 ml) until acid-free.…”

Section: Methodsmentioning

confidence: 99%

Synthetic Studies on d-Biotin, Part 9. An Improved Asymmetric Synthetic Route to d-Biotin via Hoffmann-Roche Lactone-Thiolactone Approach

Chen

Jia

Chen

et al. 2005

CHEMICAL & PHARMACEUTICAL BULLETIN

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The development of efficient processes for the total synthesis of d-biotin (1), continues to be an attractive goal in synthetic organic chemistry, because of its unique structural features, significant biological properties and commercial importance. [2][3][4][5][6][7][8] Despite great advances [9][10][11][12][13][14][15][16][17][18][19][20][21] in total synthesis over the past 55 years, large-scale preparation of this vitamin employing the F. Hoffmann-La Roche lactone-thiolactone approach, developed by Goldberg and Sternbach in 1949, still retains technically and economic advantages.22) However, a long-standing problem in this synthesis has been the lack of an efficient and convenient procedure for the desymmetrization of dicarboxylic acid 2 to form (3aS,6aR)-lactone (6). Our recent strategy, using a polymer-supported oxazaborolidine catalyzed enantioselective reduction of mesocyclic imide approach, allowed us to prepare (3aS,6R,6aR)-hydroxylactam 5 from 2 in high yield and excellent enantiomeric excess.23) However, this procedure is impractical for large-scale synthesis due to the use of expensive and toxic BF 3 · Me 2 S as the reducing agent which requires a lot of precautions, and lack of a stable polymer-supported chiral ligand.24) These obstacles prompted us, as part of our strategy to develop a new oxazaborolidine-catalyzed reducing system that can easily be employed and that gives high enantiomeric excess for a large-scale conversion of 4 into 5 as a precursor for the formation of 6, to complete the asymmetric synthesis of 1.In the present paper, we describe an efficient and practical asymmetric total synthesis of 1 starting from commercially available dicarboxylic acid 2 through an improved enantioselective reduction of meso-cyclic imide 4 with the use of recoverable chiral polymer-supported oxazaborolidine as a catalyst. Results and DiscussionThe asymmetric synthesis of 1 is presented in Chart 1. The known meso-cyclic-1,2-dicarboxylic anhydride 3 was prepared in almost quantitative yield by heating 2 in xylene with a catalytic amount of Ac 2 O with azeotropic removal of H 2 O for 13 h. Treatment of 3 with benzylamine in toluene under reflux for 6 h afforded the meso-cyclic imide 4 in a 90% yield.Next, we embarked upon the development of an efficient and convenient strategy for the large-scale asymmetric borane reduction of 4 into (3aS,6R,6aR)-hydroxylactam 5 using a chiral polymer-supported oxazaborolidine derived from polymer-supported ligand 10 25) (containing 0.39 mmol of diaryprolinol function units/g of polymer by elemental analysis) with in situ generated borane from cheap and convenient hydritic reagents and boron halide etherates. Thus, the mesocyclic imide 4 was treated with 80% NaH and BF 3 · Et 2 O in the presence of 10 under reflux in anhydrous THF to afford 5 in 82% yield. The enantiomeric excess of 5 was measured to be Ͼ98% by HPLC analysis using a Chiralcel OD column (eluent : hexane/2-propanol, 6 : 4, 0.7 ml/min).As pointed out in a number of studies, 26-32) one of the major advantages ...

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“…Since separation of the alcohol product from the chiral amino alcohol (catalyst precursor) can be difficult [4], metal [5,6] or polymer [7,8,9,10,11,12,13,14] supported oxazaborolidines have been considered. The immobilisation was achieved through a covalent bond between the support and one of the substituents of the oxazaborolidine.…”

Section: Introductionmentioning

confidence: 99%

“…The immobilisation was achieved through a covalent bond between the support and one of the substituents of the oxazaborolidine. Therefore under heterogeneous conditions the substituent chosen to anchor the enantioselective inductor also influences the enantioselective properties [10,11,12,13,14] (Figure 2).…”

Section: Introductionmentioning

confidence: 99%

Enantioselectivity Induced by Oxazaborolidine Supported on Mesoporous Silica or by Its Analog in Homogeneous Phase

2010

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Abstract:The impact of immobilization of oxazaborolidines supported on silica via different substituents on the boron and nitrogen atoms is evaluated in the enantioselective reduction of acetophenone. The performances of the homogeneous analog oxazaborolidines and silica-supported ones are compared by varying different parameters. This article deals with the synthesis, characterization and catalytic evaluation of silicasupported oxazaborolidines, their recycling capabilities and regeneration limitations.

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Oxazaborolidines as Functional Monomers: Ketone Reduction Using Polymer-Supported Corey, Bakshi, and Shibata Catalysts

Cited by 41 publications

References 12 publications

New 3,3′[2,2′-oxy-bis-(oxazaborolidine)]-ethylenes. Structural studies by NMR, X-ray, and quantum chemistry methods

New 3,3′[2,2′-oxy-bis-(oxazaborolidine)]-ethylenes. Structural studies by NMR, X-ray, and quantum chemistry methods

Synthetic Studies on d-Biotin, Part 9. An Improved Asymmetric Synthetic Route to d-Biotin via Hoffmann-Roche Lactone-Thiolactone Approach

Enantioselectivity Induced by Oxazaborolidine Supported on Mesoporous Silica or by Its Analog in Homogeneous Phase

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