Construction of Single Stereocenters

Haifeng Du at the Chinese Academy of Sciences reported (J. Am. Chem. Soc. 2013, 135, 6810. DOI: 10.1021/ja4025808) the borane-catalyzed asymmetric hydrogenation of imine 1 using diene 3 as a chiral ligand for boron. A single-enzyme cascade for the reductive transamination of acetophenone (4) with amine 5 to produce enantiopure sec-phenethylamine (6) was developed (Chem. Commun. 2013, 49, 161. DOI: 10.1039/C2CC37232K) by Per Berglund at the KTH Royal Institute of Technology in Sweden. A group at Boehringer Ingelheim in Ridgefield, Connecticut led by Jonathan T. Reeves disclosed (J. Am. Chem. Soc. 2013, 135, 5565. DOI: 10.1021/ja402647m) a procedure for the addition of DMF anion to N-sulfinyl imine 7 to furnish tert-leucine amide 8 with high diastereoselectivity. The tertiary carbinamine 10 was synthesized (Org. Lett. 2013, 15, 34. DOI: 10.1021/ol3029324) via the carbolithiation/rearrangement of vinylurea 9 as reported by Jonathan Clayden at the University of Manchester.

Gregory C. Fu at Caltech reported (Angew. Chem. Int. Ed. 2013, 52, 2525. DOI: 10.1002/anie.201208957) that the chiral phosphine 12 catalyzed the enantioselective addition of trifluoroacetamide to allene 11 to produce γ-amino ester 13 in enantioenriched form. Adeline Vallribera at the Autonomous University of Barcelona found (Org. Lett. 2013, 15, 1448. DOI: 10.1021/ol400136y) that a europium pybox complex effected the highly enantioselective α-amination of α-ketoester 14 to generate 15 on the way to the Parkinson’s disease co-drug L-carbidopa.

Hisashi Yamamoto at the University of Chicago and Chubu University reported (J. Am. Chem. Soc. 2013, 135, 3411. DOI: 10.1021/ja401182a) that a halfnium(IV) complex of the bishydroxamic acid 17 catalyzed the enantioselective epoxidation of the tertiary homoallylic alcohol 16. The rearrangement of the allylic carbonate 19 to produce allyl ether 21 with high ee under iridium catalysis in the presence of ligand 20 was disclosed (Org. Lett. 2013, 15, 512. DOI: 10.1021/ol3033237) by Hyunsoo Han at the University of Texas at San Antonio.

The asymmetric vinylogous aldol reaction of 3-methyl-2-cyclohexen-1-one (22) and α-keto ester 23 to furnish tertiary carbinol 25 using the bifunctional organocatalyst 24 was developed (Org. Lett. 2013, 15, 220. DOI: 10.1021/ol303312p) by Paolo Melchiorre at ICREA and ICIQ in Spain. The enantioselective catalytic addition of methyl Grignard to nonanal (26) using ligand 27 in the presence of excess titanium(IV) isopropoxide was reported (Adv. Synth. Catal. 2013, 355, 1249. DOI: 10.1002/adsc.201201117) by Beatriz Maciá at Manchester Metropolitan University and Miguel Yus at Alicante University in Spain.

Chun-Jiang Wang at Nankai University found (Org. Lett. 2013, 15, 3448. DOI: 10.1021/ol4015305) that thiourea 30 catalyzed the enantioselective conjugate addition of thiophenol to ester 29. Kazuaki Ishihara at Nagoya University demonstrated (Angew. Chem. Int. Ed. 2013, 52, 4549. DOI: 10.1002/anie.201300938) that a cooperative catalyst complex derived from BINOL (33) and dibutylmagnesium with water catalyzed the highly enantioselective addition of diphenylphosphine oxide to ester 32 to furnish 34.

Finally, Takashi Ooi at Nagoya University reported (Chem. Sci. 2013, 4, 1308. DOI: 10.1039/C2SC22027J) that the addition of azlactone 37 to methyl propiolate can lead to either the E-product 35 or the Z-product 39 with high enantioselectivity using catalysts 36 or 38 respectively. Selectivity for the isomeric products is proposed to arise by control of the protonation pathway of the intermediate allenic enolates that result from the conjugate addition step.