Scalable synthesis of enantiomerically pure syn2,3. Synthesis of chiral acyclic nucleosides by sharpless. This document was downloaded for personal use only. The sharpless asymmetric epoxidation converts alkenes into chirally active epoxides innumerable syntheses published that use the sae chiral epoxides easily converted into. Asymmetric dihydroxylation and aziridination of allenes. Request pdf an improved version of the sharpless asymmetric dihydroxylation the osmium catalyzed asymmetric dihydroxylation of olefins sharpless ad was studied under controlled ph conditions.
Sharpless asymmetric epoxidation the sharpless epoxidation is an organic reaction used to steroselectively convert an allylic alcohol to an epoxy alcohol using a titanium isopropoxide catalyst, tbutyl hydroperoxide tbhp, and a chiral diethyl tartrate det. Enantioselective cisdihydroxylation of olefins using osmium catalyst in the presence of. Catalytic asymmetric dihydroxylation of alkenes aims of the experiment to prepare an enantiomerically enriched 1,2diol using sharpless catalytic asymmetric dihydroxylation procedure, and to estimate the enantiomeric purity of the material you obtain. Sharpless asymmetric reactions require an osmonium catalyst and a. Mechanism, references and reaction samples of the sharpless asymmetric dihydroxylation. In this example, excess tbhp was quenched with triethylphosphite instead of feii sulfate.
The mnemonic device for predicting the face selectivity 1. The sharpless asymmetric dihydroxylation protocol, using enriched admix. A study in the correlation of the enol ether chain length and enantioselectivity. Part of thebiochemistry commons, and thechemistry commons this dissertation is brought to you for free and open access by byu scholarsarchive. The synthesis starts from 4methoxystyrene 9, a commercially available starting material. Barry sharpless, who was awarded the nobel prize in chemistry in 2001 for his work. Epoxidation, dihydroxylation, and the utility of epoxides and diols ready outline.
Although there are many routes to accomplish this oxidation, the most common and direct processes use a highoxidationstate transition metal typically osmium or manganese. Multigramme synthesis and asymmetric dihydroxylation of a. Sharpless asymmetric dihydroxylation continued youtube. Sharpless asymmetric dihydroxylation is a stereoselective reaction that is known to be extremely reliable. This reaction is used to break a double bond and add two hydroxyl groups in a cis manner. Applications of sharpless asymmetric dihydroxylation in. Sharpless asymmetric dihydroxylation also called the sharpless bishydroxylation is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol.
Asymmetric dihydroxylation reactions were then used to transform the butenoate, ultimately into all four. Ligands such as pyridine accelerate the osmylation of olefins criegee, r marchand, b. Asymmetric dihydroxylation of alkenes can be modified to synthesize chiral amino alcohols, 429 in what is known as sharpless asymmetric aminohydroxylation or oxyamination. Racemic dihydroxylation of alkenes is efficiently accomplished with catalytic osmium added as oscl 3, stoichiometric k 3 fecn 6 and quinuclidine under conditions similar to those of the sharpless asymmetric hydroxylation. Sharpless is regarded as the developer of stereoselective oxidation reactions in the field of click chemistry sharpless received the scheele award in the year of 1991, arthur c. Asymmetric synthesis of cyclic hydroxy ketones derived from enol ethers via sharpless asymmetric dihydroxylation. Multigramme synthesis and asymmetric dihydroxylation of a 4. The sharpless catalytic asymmetric dihydroxylation ad of ole. Karl barry sharpless is an american chemist and nobel laureate born on april 28, 1941. Inorganic chemistry organic chemistry nobel prize cinchona alkaloid asymmetric dihydroxylation these keywords were added by machine and not by the authors.
Karl barry sharpless developed stereoselective oxidation. Ligands such as pyridine accelerate the osmylation of ole. Download hires imagedownload to mspowerpointcite this. Sharpless dihydroxylation request pdf researchgate. Myers sharpless asymmetric epoxidation reaction chem 115 a further example of anomalous stereochemistry in ae of an allylic diol no reaction with dipt.
Cope award in the year of 1992, tetrahedron prize in the year of 1993, king faisal international prize. Request pdf an improved version of the sharpless asymmetric dihydroxylation the osmium catalyzed asymmetric dihydroxylation of olefins. We briefly investigated conditions to shorten the reaction time. Sharpless asymmetric dihydroxylation reaction is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to provide an optically active vicinal diol.
The osmium catalyzed asymmetric dihydroxylation sharpless ad has. Sharpless asymmetric dihydroxylation on an industrial scale. Sharpless asymmetric dihydroxylation sharpless ad chem. Relatively large volumes of organic extractant were necessary to isolate the highly watersoluble product, and chromatographic. This reaction is a transformation of olefins into syn. Myers sharpless asymmetric dihydroxylation reaction chem.
This process is experimental and the keywords may be updated as the learning algorithm improves. An asymmetric dihydroxylation route to soxybutynin. Rama rao arkivoc 2005 iii 3643 issn 14246376 page 38 arkat usa, inc the synthetic route to rtembamide 2 and raegeline 3 is shown in scheme 2. Sad is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form an optically pure vicinal diol. The benefits of the optimized sharpless asymmetric dihydroxylation reactionexcellent yield and enantioselectivitywere somewhat offset by the length of the reaction time in the optimized protocol 5 d, referred to as method a table 2, entry 1. Sharpless asymmetric dihydroxylation ligands were synthesized using a triazine spacer group in two, high yielding steps and gave good enantioselectivities in the asymmetric dihydroxylation of alkenes. Reaction conditions the catalytic asymmetric dihydroxylation is performed in a 1. The corresponding isolated yields under these conditions.
These keywords were added by machine and not by the authors. Asymmetric dihydroxylation an overview sciencedirect. S patent 4,871,855, 1989 assigned to the massachusetts institute of technology. The corresponding isolated yields under these conditions were 54%. Enantioselective cis dihydroxylation of olefins using osmium catalyst in the presence of cinchona alkaloid ligands. The reaction has been applied to alkenes of virtually. Mechanism of the sharpless asymmetric dihydroxylation. The reason that they attach in a cis manner is because of how the reaction occurs. Asymmetric dihydroxylation of 9 with dhqd2phal ligand gave the diol 10 in 93% yield and. Asymmetric dihydroxylation of 1hexene using diferent surfactants at 0.
The extension of this synthetic method to other olefins is also presented. Jm chong and kb sharpless nucleophilic opening of 23 epoxy. Coster, in strategies and tactics in organic synthesis, 2004. Asymmetric dihydroxylation of alkenes is one of the fundamental reactions in organic synthesis, but the antidihydroxylation is much less developed than. The journal of organic chemistry 2003, 68 21, 80888091. The sharpless lab was the first academic chemistry group with robotics, and the lesson from the combinatorial numbers game was the primacy of reliability. Meo2cme2, pocl3 ochph 2 sph o o paynerearrangement. Sharpless asymmetric dihydroxylation springerlink skip to main content.
Two catalytic cycles operate in the osmiumcatalyzed olefin dihydroxylation and aminohydroxylation. Csir net chemical science solved question june 2017,woodward reaction and prevost reaction in hindi duration. Examples of the sharpless asymmetric epoxidation reaction in industry. Sharpless asymmetric epoxidation mcmaster university. An improved version of the sharpless asymmetric dihydroxylation. The metal is often used as a catalyst, with some other stoichiometric oxidant present. This page was last edited on 12 october 2019, at 22.
The sharpless asymmetric dihydroxylation or sad is a both a wellknown and reliable method for generating an excess of one enantiomer. Molybdenumcatalyzed asymmetric anti dihydroxylation of allylic. Asymmetric dihydroxylation and aziridination of allenes and related chemistry renmao liu brigham young university provo follow this and additional works at. The sharpless catalog library ccd images using color and narrowband filters. The power of the sharpless asymmetric dihydroxylation is best illustrated by the ex. Sharpless asymmetric dihydroxylation an overview sciencedirect. Sharpless asymmetric dihydroxylation is the chemical reaction of an alkene with osmium. Molybdenumcatalyzed asymmetric anti dihydroxylation of. Sharpless asymmetric dihydroxylation of olefins in. It is common practice to perform this reaction using a. Turnover is achieved by reoxidation with stoichiometric oxidants. An asymmetric dihydroxylation reaction was performed using the improved sharpless conditions with the newer aqn based ligands, producing excellent ees for both enantiomers of the diol, 95% for the enantiomer derived from admix. Sharpless, procedure for the catalytic asymmetric epoxidation of allylic alcohols in the presence of molecular sieves, j. Our reaction complements the sharpless dihydroxylation not only in its diastereoselectivity, but also in regiocontrol.
During our work on the osmium catalyzed dihydroxylation of olefins with molecular. An asymmetric dihydroxylation route to roctopamine. Dihydroxylation is the process by which an alkene is converted into a vicinal diol. Diepoxide 510 has been converted into alditol 512 and thioalditols 5 and 514. High reaction yields and high product enantioselectivities have been reported for a broad range of ole. A range of chiral acyclic nucleosides with two adjacent hydroxyl groups present on the side chains could be produced in good yields up to 97% yield and excellent enantioselectivities 9099% ee. Slow hydrolysis of the osvi monoglycolate or monoazaglycolate in aminohydroxylation intermediate often results in the addition of another molecule of olefin thereby shunting the catalysis into the second catalytic cycle. Myers sharpless asymmetric epoxidation reaction chem 115. I was hoping some of you chemistry masters could help a girl out. Lab d sad lab d sharpless asymmetric dihydroxylationad.
Application of the sharpless asymmetric dihydroxylation methodology to the enantioselective preparation of 2,3. The literature value is around 90%, but i only got 50%. An efficient method to construct chiral acyclic nucleosides via sharpless asymmetric dihydroxylation of nallylpyrimidines or nalkenylpurines is reported. The dhq2aqn and dhqd2aqn ligands described by sharpless were the most effective.
The aim of this study is to present the applications of sharpless asymmetric dihydroxylation sad also called the sharpless bishydroxylation. Barry sharpless scripps won the noble prize in chemistry in 2001 for the development of catalytic asymmetric oxidation reactions such as this dihydroxylation and the sharplesskatsuki epoxidation. Epoxidation condensation approaches darzens condensation sulfur ylides with organic peroxides peroxy acids peroxy iminic acids dioxiranes dmdo enantioselective versions metalcatalyzed approaches voacac 2 sharpless ae metal oxos mto fe, pt and mnbased. Myers sharpless asymmetric dihydroxylation reaction chem 115.
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