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Sharpless Asymmetric Epoxidation i. Mechanism ii. Scope Sharpless Asymmetric Dihydroxylation i. Catalytic Cycle ii. Mechanism iii. Scope Sharpless Asymmetric Aminohydroxylation . Asymmetric Epoxidation - Substrate Sco pe Mneumonic for Predicting Enantiofacial Selectivity! Ti-catalyzed AE is compatible with a majority of functional groups

1.4.3 Enantiopure p-aminoalcohols in the asymmetric Michael 27 addition. 1.4.4 Cz-symmetric ligands in the catalytic enantioselective 32 Michael addition. 1.5 Asymmetric epoxidations 35 1.5.1 The Katsuki-Sharpless asymmetric epoxidation 35 1.5.2 The Oxone asymmetric epoxidation 38 1.5.3 The Julia-Colonna asymmetric epoxidation 41

Example of enantioselective synthesis using asymmetric induction is the Sharpless dihydroxylation reaction where the chirality of the product can be controlled by the "AD-mix". 21. . Sharpless Asymmetric Epoxidation 27. Generally, Sharpless asymmetric dihydroxylation favors oxidation of the more electron-rich alkene.

Sharpless Asymmetric Epoxidation (SAE) Sharpless asymmetric epoxidation was the first general asymmetric catalyst There are a large number of practical considerations that we will not discuss Suffice to say it works for a wide range of compounds in a very predictable manner 14 EtO2C CO2Et OH OH (-)-DET

1.1.1 Sharpless epoxidation Barry Sharpless was awarded the 2001 Nobel Prize for his contributions in stereoselective oxidations of olefins (epoxidation, dihydroxylation, aminohydroxylation). . Another contribution of Sharpless in the field of asymmetric catalysis is the asymmetric dihydroxylation In the case with K 3 Fe(CN) 6

to approach the double bond for the epoxidation. This reaction generally occurs in high yield (70-90%) with outstanding enantioselectivity (up to 99% e.e.) The Sharpless asymmetric epoxidation (SAE) has proven to be one of the most versatile reactions in synthetic chemistry.6 Scheme 1: Sharpless Asymmetric Epoxidation (SAE Reaction). R2OH R1 R3

Another transformation of high synthetic utility is asymmetric epoxidation. There exist a number of asymmetric epoxidations in the literature, including the Sharpless epoxidation, the Jacobsen-Katsuki epoxidation and the Juliá-Colonna Epoxidation. These methods have one major drawback in that they require very specific functionality in order .

of the most common examples to demonstrate the concept of enantioselective reactions is Sharpless asymmetric epoxidation in which allyl alcohols are converted into epoxy alcohols via a complex cycle. The typical catalytic cycle of the Sharpless asymmetric epoxidation is shown below. Buy the complete book with TOC navigation,

The Sharpless Asymmetric Epoxidation. This reaction has become one of the most widely used and important epoxidation reactions. The method involves the use of Ti(Oi-Pr)4 and tert-butyl hydroperoxide in the presence of either D-(-)-diethyltartrate or L-( )-diethyltartrate. The facial preference for asymmetric epoxidations of

Keywords: Asymmetric epoxidation, Chalcone, Quaternary sugar salts, Nonionic surfactants Introduction Although, sharpless paved the way for much of today's catalytic asymmetric syntheses1, the use of phase-transfer catalysts in asymmetric synthesis was described 2-6 in the mid-1970s.

1.1 Sharpless asymmetric epoxidation In 1980 prof. Sharpless and prof. Katsuki published the first article dealing with newly discovered enantioselective epoxidation of allylic alcohols by organic hydroperoxides catalysed by titanium(IV) complexes of enantiopure esters of tartaric acid (Scheme 1) [1,2]. Scheme 1 General scheme of Sharpless .

Diastereoselective Epoxidation and Aziridination Reactions Russell C. Smith Denmark Group Meeting February 15, 2005. Epoxidation Chemistry Traditional epoxidation methods Enantioselective epoxidation -Sharpless -Transition metal O -Manganese Salen Complexes H2O2/ MeOH . Asymmetric Aziridination- Use of in situ prep of diazo .

Sharpless Asymmetric Epoxidation: OH ( )-DET, Ti(OiPr)4 t-BuOOH OH O Moreelectron rich double bond participated in epoxidation Epoxidation. CH-401 Course on Organic Synthesis; Course Instructor: Krishna P. Kaliappan 31 Epoxidation Directed by Polar Group Hydrogen bonding between the hydroxyl group and the reagent

Examples of the Sharpless Asymmetric Epoxidation Reaction in Industry: In this example, excess TBHP was quenched with triethylphosphite instead of FeII sulfate. In this example, a stoichiometric amoun

The Sharpless Asymmetric Epoxidation converts alkenes into chirally active epoxides Innumerable syntheses published that use the SAE Chiral epoxides easily converted into: -12 D, osil - Make carbon-carbon bonds (stereospecifically) - Aminoalcohols Two examples considered: - A complex synthesis of Venustatriol by EJ Corey

The Sharpless asymmetric epoxidation can be employed to synthesize different pheromones, leukotrienes, saccharides, terpenes, and antibiotics. Buy the complete book with TOC navigation, high resolution images and no watermark. LEGAL NOTICE This document is an excerpt from the book entitled "A

1.2 The Sharpless asymmetric epoxidation reaction: 1.2.1 Introduction: The Sharpless asymmetric epoxidation procedure is currently the leading method for preparing a chiral epoxide. The system uses ( ) or ( ) diethyl tartrate, Ti(O i-Pr)4 and t-BuOOH, all of which are commercially available. 4 This system has been very successful.

The Scheme below begins with a Sharpless asymmetric epoxidation. The product is then tosylated followed by a nucleophilic displacement with Bn 2NH to give A. Treatment of A with TMSOTf leads to an aza-Payne rearrangement sequence that affords B in 90% yield. (a) For the desired Sharpless asymmetric epoxidation, what diethyl tartrate ( or .

1.2 The Sharpless asymmetric epoxidation reaction: 1.2.1 Introduction: The Sharpless asymmetric epoxidation procedure is currently the leading method for preparing a chiral epoxide. The system uses ( ) or ( ) diethyl tartrate, Ti(O i-Pr)4 and t-BuOOH, all of which are commercially available. 4 This system has been very successful.

K. B. Sharpless 3 Nobel Laureate K. Barry Sharpless became W. M. Keck Professor . Asymmetric epoxidation Asymmetric dihydroxylation Asymmetric aminohydroxylation. Click Chemistry 4-Robust connection-High functional group tolerance-Fast kinetics-Easy operation Nat. Rev. Chem. 2018, 2, 202.

Shi Asymmetric Epoxidation Kinetic Resolution of racemic 1,3- and 1,6-disubstituted cyclohexenes provides optically enriched allylic Silyl ethers OTMS Ph 35 mol% 1 49% conv. OTMS Ph . Sharpless Asymmetric Dihydroxylation Reaction Catalytic Cycle: OOs O O O L OOs O O L L OOs O O O L 2 H 2O, 2HO-H 4OsO 6 2- HO HO L VIII VI 2 Fe(CN) 6 4-2 Fe(CN .

in asymmetric organic synthesis and medicinal chemistry [7]. Since the development of the asymmetric epoxidation of allylic alcohols by Sharpless in the early 1980s [8], considerable efforts were devoted to the development of an efficient catalytic system for asymmetric epoxidation of olefins in the last two decades [9].

Sharpless Asymmetric Epoxidation Mitsunobu Reaction Stille Coupling TBDMSO OH 4 O O Br OR RO 7 SnBu 3 Bu3Sn 11 OH 3 TBDMSO OH TBDMSO OH O Sharpless Epoxidation HO O Bu3Sn OMOM 4 5 6. Lett's Total Synthesis Resorcinylic Macrolides First Total Synthesis O O Cl O Me MeO 7 O O Cl TBDMSO 8 TBDSO 6 8 PdCl 2(CH 3CN) 2 PPh3, DME O O TBDMSO 9 O HO .

Studies on epoxidation using molybdenum(VI) compounds have contributed to the development of significant stereoselectivity and e ciency of conducted reactions. Unfortunately, the use of solvent-free epoxidation reactions remains to be explored. 2.3. Sharpless System for Asymmetric Epoxidation of Olefins with Hydroperoxide with Dimeric Titanium

Sharpless asymmetric epoxidation (T. Katsuki and K. B. Sharpless) Asymmetric hydrogenation (W. Knowles, H. Kagan, R. Noyori) Evans aldol reaction Olefin metathesis (Y. Chauvin, T. J. Katz, R. Schrock, R. Grubbs, N. Calderon) 7. In the box below, describe (150 words or less) the Drug Discovery and Development Process indicating

1-14 Illustration of the asymmetric epoxidation using the Sharpless method. Use of the ( ) or (-)-tartrate allows for the oxygen atom to be added to only one face of . used by Shi30 for the asymmetric epoxidation of alkenes using peroxymonosulfate to generate a dioxirane in situ .

asymmetric dihydroxylation 73% H3C O NHFmoc H3C O OH O H3C CH3 O HN O O CCl3 CH3 OH Cl OCH3 O HN N O H CH3 Cl H3C O OCH3 H3C O O O H3C CH3 O HN O O CCl3 CH3 O Cl H3C O OCH3 H3C O O CH3 CH3 NHFmoc O HN O O CCl3 3 OH R O The Shi epoxidation system provided the desired epoxide in a 6:1 diastereomeric ratio, while other epoxidation methods never .

3.2 Sharpless Resolution - racemic allylic alcohols as substrates in an asymmetric epoxidation; creates an additional stereocenter! - one enantiomer is epoxidized faster than the other one Sharpless JACS 1981, 103, 6237 3.3 Oxidative KR of secondary alcohols - Pd-catalyzed aerobic oxidative kinetic resolution n JACS 2002 124, 8202

blocks together to make a larger structure. K Barry Sharpless and his co-workers have discovered and developed many widely used catalytic oxidation processes including the first general methods for stereoselective oxidation the Sharpless reactions for asymmetric epoxidation, dihydroxylation, and aminohydroxylation of olefins. His

tion of the Sharpless asymmetric epoxidation,2 there has been an ever-increasing demand for catalyst-controlled processes that allow efficient and predictable access to enantioenriched oxiranes. Significant efforts to expand the scope of such catalytic epoxidations have been made via the seminal contributions of Jacobsen3 and Katsuki4 using

Sharpless Asymmetric Epoxidation Epoxidation is a reaction with forms an epoxide ring. 27 The origin of the stereoselectivity lies essentially in steric hindrance: Heterogeneous Catalysis Most industrial processes are of this type, involving reactions of gases on solid surfaces. Reactants

ligand was formulated that could be recovered post-epoxidation in good yield by relatively simple solvent manipulations. This recovered ligand could then be re-used without significant loss in enantioselectivity and represented the synthesis of a recoverable ligand for the Sharpless asymmetric epoxidation, a leader in the field.

allylic epoxides 22a d. Their synthesis relied on Sharpless asymmetric epoxidation of the corresponding allylic alcohols 21a c (Scheme 4).[20] Thus, while epoxidation precursors 21b and 21c were known,[21] allylic alcohol 21a was prepared by means of a short synthetic route, involving Stille coupling of vinyl stan-

an early-stage epoxidation and diketopiperazine-forming macrocyclization was pursued (Scheme 5). Thus, 3a-allyl pyrroloindoline 23 was converted to allylic alcohol 39 in two steps. Sharpless asymmetric epoxidation delivered epoxy alcohol 40 in 10:1 dr, 14 which was converted to mesylate 41. Concomitantly, amine 43 was prepared from endo-

Sharpless epoxidation TBSCl Active areas of research at that time Hydroboration Controlling enolate geometry Organic photochemistry Cross-coupling reactions. Key Research Programs in Total Synthesis . All stereocenters set by asymmetric aldol, alkylation or epoxidation OR HO HO Me

2.6 Chiral Catalyst-Induced Aldehyde Alkylation: Asymmetric Nucleophilic Addition 107 2.7 Catalytic Asymmetric Additions of Dialkylzinc to Ketones: Enantioselective Formation of Tertiary Alcohols 118 2.8 Asymmetric Cyanohydrination 118 2.9 Asymmetric a-Hydroxyphosphonylation 124 2.10 Summary 127 2.11 References 127 3 Aldol and Related Reactions 135

N Myers Sharpless Asymmetric Dihydroxylation Reaction Chem 115 Reviews: Ligands such as pyridine accelerate the osmylation of olefins (Criegee, R.; Marchand, B.; Wannowius, H. Liebigs Ann. Chem. 1942, 550, 99-133.) Catalytic Cycle: Turnover is achieved by reoxidation with stoichiometric oxidants:

Sharpless asymmetric epoxidation examples OH Ti(Oi-Pr)4 t-BuOOH ( )-DET OH O 85% yield 94% ee Bn O O OH Ti(Oi-Pr)4 t-BuOOH ( )-DET Bn O O OH O Ti(Oi-Pr) 4 and DET are used catalytically (1-5%), but t-BuOOH, as the source of the epoxide oxygen atom, must be used stoichiometrically Only allylic alcohols are epoxidized by these reagents

Sharpless Asymmetric Epoxidation - Racemic allylic alcohols are treated with a half equivalent of terr-butyl hydroperoxide in the presence of chiral catalysts, titanium tetraisopropoxide complexed with D- or L-ethyl tartrate. R3 R2 R1 OH Ti[iPrO)4 OOH R3 R2 R1 OH O R2 R3 R1

The Asymmetric Baeyer-Villiger Oxidation Traditional Synthetic Methods Versus Enzymes Craig Seymour (cseymou2 at illinosi.edu) Group Meeting Presentation 16 July 2013 Online Version . . Lopp's Use of Sharpless' Epoxidation Conditions 23 Lopp, 1996, 1998: Use of TADDOL