α,β-Aziridinylphosphonates by lithium amide-induced phosphonyl migration from nitrogen to carbon in terminal aziridines

• David. M. Hodgson and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2010, 6, 978–983, doi:10.3762/bjoc.6.110

• or BF3•Et2O in CH2Cl2; aminolytic kinetic resolution [12][38]), and use of (Me3)SiHNPO(OEt)2 [39] also proved ineffective. A convenient asymmetric access was eventually developed, starting with ring-opening of commercially available (R)-1,2-epoxybutane (15) using ammonia, which gave β-amino alcohol

Development of dynamic kinetic resolution on large scale for (±)-1-phenylethylamine

• Lisa K. Thalén and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2010, 6, 823–829, doi:10.3762/bjoc.6.97

• Lisa K. Thalen Jan-E. Backvall Stockholm University, Department of Organic Chemistry, Arrhenius Laboratory SE-106 91, Stockholm, Sweden 10.3762/bjoc.6.97 Abstract Candida antarctica lipase B (CALB) and racemization catalyst 4 were combined in the dynamic kinetic resolution (DKR) of (±)-1

• donor. Keywords: dynamic kinetic resolution; kinetic resolution; racemization; Shvo; Candida antartica lipase B; Introduction Chiral amines are important building blocks in the synthesis of many pharmaceuticals, fragrances, and agricultural products, and it is therefore important to develop methods

• amination of prochiral ketones [8]. Of these methods kinetic resolution using enzymes is often favored due to its simplicity [9][10]. The main disadvantages of kinetic resolution are that only a maximum yield of 50% can be achieved and that the remaining unreacted starting material must be removed from the

Three step synthesis of single diastereoisomers of the vicinal trifluoro motif

• Vincent A. Brunet,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2009, 5, No. 61, doi:10.3762/bjoc.5.61

• . Results and Discussion The chemistry was initiated from allylic alcohol 2 which can readily be prepared in enantiomerically pure form by hydrolytic kinetic resolution of vinyl epoxide 1 following Jacobsen’s protocol [13] (Scheme 3). Diol 2 was converted to tosyl ester 3 in a regioselective manner

Asymmetric reactions in continuous flow

• Xiao Yin Mak,
• Paola Laurino and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2009, 5, No. 19, doi:10.3762/bjoc.5.19

• co-workers have designed a continuous-flow reactor system, PASSflow [40], based on the use of a functionalizable monolithic rod derived from a glass/polymer composite. This device was used for the dynamic kinetic resolution of epibromohydrin 32, using a monolith reactor functionalized with a chiral

• , larger scale run (10 mmol) was performed continuously over a 6 day period (until complete consumption of epibromohydrin), providing the desired (R)-diol 34 also in similar yield and enantioselectivity. The hydrolytic kinetic resolution of a terminal epoxide in continuous flow has also been investigated

• have been developed recently, including processes using alternative solvents such as ionic liquids and/or scCO2 [56][57][58][59][60][61]. The kinetic resolution of racemic 1-phenylethanol 54 was performed continuously in scCO2, using an immobilized lipase (Candida antarctica, Novozym 435) and vinyl

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• the kinetic resolution manifold, providing the key bis-THF fragment 316 as a single diastereomer. Protodesilylation of the bis-THF 316 was accomplished by treatment with TBAF to give tetraol 317. The butenolide ring was then installed completing the total synthesis of (+)-bullatacin (311). In 2006

Diastereoselective and enantioselective reduction of tetralin- 1,4-dione

• E. Peter Kündig and
• Alvaro Enriquez-Garcia

Beilstein J. Org. Chem. 2008, 4, No. 37, doi:10.3762/bjoc.4.37

• precedent for procedures for the asymmetric synthesis of 9. The first involves as the key step kinetic resolution by enzymatic hydrolysis of the corresponding acetate with porcine pancreatic lipase giving (−)-9 in 47% yield and 95% ee [13]. A second approach uses a Pd-catalyzed asymmetric oxidation of meso

Large- scale ruthenium- and enzyme- catalyzed dynamic kinetic resolution of (rac)-1-phenylethanol

• Krisztián Bogár,
• Belén Martín-Matute and
• Jan-E. Bäckvall

Beilstein J. Org. Chem. 2007, 3, No. 50, doi:10.1186/1860-5397-3-50

• Krisztian Bogar Belen Martin-Matute Jan-E. Backvall Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden 10.1186/1860-5397-3-50 Abstract The scale-up of the ruthenium- and enzyme-catalyzed dynamic kinetic resolution (DKR) of (rac)-1

• ][28] and recently this approach has been extended to dynamic kinetic resolution (DKR) by combining the enzymatic resolution with a metal-catalyzed racemization. [29][30][31][32][33][34][35][36][37] Today, many stable lipases are commercially available and they are frequently used in synthetic organic

• . Experimental See Supporting Information File 1 for experimental data. Racemization catalyst 1. DKR of 1-phenylethanol under an Ar atmosphere (top) and DKR of 1-phenylethanol under an O2 atmosphere (bottom). Dynamic kinetic resolution of 1-phenylethanol (2) under different reaction conditions.a Supporting

Conformational rigidity of silicon- stereogenic silanes in asymmetric catalysis: A comparative study

• Sebastian Rendler and
• Martin Oestreich

Beilstein J. Org. Chem. 2007, 3, No. 9, doi:10.1186/1860-5397-3-9

• metal-catalyzed asymmetric transformations as exemplified by (1) the hydrosilylation of alkenes constituting a chirality transfer from silicon to carbon and (2) the kinetic resolution of racemic mixtures of alcohols by dehydrogenative silicon-oxygen coupling. In this investigation, a cyclic and a

• were reported, [6] namely the inter- [7] as well as intramolecular [8] chirality transfers from silicon to carbon. Moreover, we had demonstrated that chiral silanes resolve racemic mixtures of alcohols in a non-enzymatic, transition metal-catalyzed kinetic resolution. [9] During our ongoing

• -catalyzed kinetic resolution of donor-functionalized alcohols capable of two-point binding. The reagent-controlled hydrosilylation of norbornene derivative 2 with silane 1a proceeds with a perfect chirality transfer (rac-1a → rac-3a, Scheme 1). [8] Mechanistic investigation of the nature of the

Towards practical biocatalytic Baeyer- Villiger reactions: applying a thermostable enzyme in the gram- scale synthesis of optically- active lactones in a two-liquid- phase system

• Frank Schulz,
• François Leca,
• Frank Hollmann and
• Manfred T. Reetz

Beilstein J. Org. Chem. 2005, 1, No. 10, doi:10.1186/1860-5397-1-10

• catalysis (Table 1). We were pleased to observe essentially identical enantioselectivities when applying in vitro catalysis (for ketone 1 compare Table 1; the kinetic resolution of ketone 6 is characterized by a selectivity factor of E = 100, the enantiopurity of lactone 7 being 95.4% ee (R)). Ketone 1

• substrate in cyclohexane. The kinetic resolution reached the optimal 50% conversion after about 24 h. Upscaling to gram-quantities was straight-forward without changes in the procedure. Overall we obtained turnover numbers (TONs) of more than 30000 for the P3-PAMO-catalyzed BV-oxidation of ketone 1, which

Mixtures of monodentate P-ligands as a means to control the diastereoselectivity in Rh-catalyzed hydrogenation of chiral alkenes

• Manfred T. Reetz and
• Hongchao Guo

Beilstein J. Org. Chem. 2005, 1, No. 3, doi:10.1186/1860-5397-1-3

• described earlier.[34] Since the substrates 1 and 5 were used as racemates, kinetic resolution may be involved when the chiral ligands are employed, i.e., diastereoselectivity may change with conversion. This aspect was not a subject of the present study. In all hydrogenation reactions the standard