Johnson-Claisen Rearrangement

The orthoester Johnson–Claisen rearrangement an important C–C bond forming reaction has been used enormously in the past four decades in the synthesis of bioactive molecules natural products synthetic intermediates analogues and useful building blocks The method has also featured in chemical modification of materials This review covers developments in this rearrangement since 2003 Utilizing a Johnson-Claisen rearrangement and an enantioselective Evans-type aldol to generate the starting fragments a series of reactions was performed to find the appropriate conditions for a key bond-forming ester enolate aldol Oxidation of the product yielded a beta-ketoester that contained the complete carbon skeleton of cornexistin Previous progress towards cornexistin included the

Johnson

Bei der Johnson-Claisen-Umlagerung handelt es sich um eine Namensreaktion in der Organischen Chemie die nach William Summer Johnson und Ludwig Claisen benannt wurde Johnson entdeckte 1970 diese Reaktion der Doppelname mit Claisen wurde auf Grund des Mechanismus gewhlt Mit dieser Umlagerung wird ein Ester synthetisiert bersichtsreaktion Bei dieser Umlagerung reagiert

Johnson-Claisen (orthoester) rearrangement 139 Clemmensen reduction 141 Combes quinoline synthesis 144 Conrad-Limpach reaction 147 Cope elimination reaction 149 Cope rearrangement 151 Oxy-Cope rearrangement 152 Anionic oxy-Cope rearrangement 153 Corey-Bakshi-Shibata (CBS) reduction 154 Corey-Chaykovsky reaction 157 Corey-Fuchs reaction 160 Corey-Kim oxidation 162

Utilizing a Johnson-Claisen rearrangement and an enantioselective Evans-type aldol to generate the starting fragments a series of reactions was performed to find the appropriate conditions for a key bond-forming ester enolate aldol Oxidation of the product yielded a beta-ketoester that contained the complete carbon skeleton of cornexistin Previous progress towards cornexistin included the

Claisen rearrangement explained Claisen rearrangement should not be confused with Claisen condensation The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen The heating of an allyl vinyl ether will initiate a [3 3]-sigmatropic rearrangement to give a γ δ-unsaturated carbonyl

Several factors affecting the allylic azide rearrangement along with some respective examples are presented Chapter two describes an efficient synthesis of azido unsaturated ester compounds using a microwave-assisted domino allylic azide / Johnson-Claisen rearrangement The domino rearrangement reaction proceeds to give the azido ester compounds in good yield and excellent

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Johnson- Claisen Rearrangement 12 12 S Johnson-Claisen 13 (S 11 (1 mol%) HC02H/Et3N BnO BnO OH OHC N02 Et02C MeO MeO MS4 i-pr2NEt 180 'C MWI 1) IBX Et02CBnO 93%ee 0 10 OHC CH Cl -78 oc -78 oc to rt OHC Et02C BnO OHC Et02C Bno CSA MeO Meo 88% ee MgCl MeO N02 MeCN reflux MeO 86% Meo NH2 R02C Bno H or Et) 2) Fe NH4Cl EtOH/H20 80 oc 90% MeO MeO

Johnson Claisen Rearrangement O OR = EtO HO O racemic O O racemic NH2 Ti(i-OPr)4 O O Ti(Oi-Pr)3 NH2 O O Ti(Oi-Pr)3 NH2 Q1 O H O Ti(Oi-Pr)3 NH HN HO O Ti(Oi-Pr)3 quench HN HO O cryst O O chiral 2M H2SO4 racemic HN HO O H2N HO O chiral OH P T O Q2 HO OH TBDPSCl HO OTBDPS Cl OMe O base O OTBDPS O OMe MeO OMe O O IrLn OTBDPS O OMe OMe O LiCl Krapcho

Nicoloau then meticulously describle each step in synthesis with referral to important named reactions such as the Noyori assymmetric reduction Luche reaction Johnson Claisen rearrangement Julia olefination etc With such didatic skill and clarity Nicoloau has taught the gist of synthesizing complex molecules from commercially available building blocks A great way to use the book and

Johnson-Claisen Rearrangement 4 Cope Rearrangement 5 Anionic oxy-Cope Rearrangement 6 Palladium-catalyzed Cope Rearrangement 7 Aza-Cope-Mannich Reaction Chapter 2 Aldol Reaction 1 Diastereoselective Aldol Reaction with Lithium Enolate 2 Diastereoselective syn-Aldol Reaction 3 Diastereoselective anti-Aldol Reaction Chapter 3 Metal Allylation Reaction 1 Boron Allylation

Synthetic Studies Towards the Anti-inflammatory Agent Oleocanthal using a Johnson-Claisen (Orthoester) Rearrangement Strategy ResearchSpace/Manakin Repository Login University Home → Library → ResearchSpace Home → A1 - Research Outputs Online → Journal Articles → View Item JavaScript is disabled for your browser Some features of this site may not work without it Synthetic

Displayed a synthetically useful domino reaction and demostrated the utility of the Johnson– Claisen rearrangement W S Johnson Johnson W S Gravestock M B McCarry B E J Am Chem Soc 1973 95 20 6832 Progesterone: Retrosynthetic Analysis Me OO OO PPh 3 I Me Me CHO Me Me Me OO OO Me Me Me O O Me Me O Me Me Me Me H Me O Me Me H H H H O Me (+)-progesterone Me

Competing researchers who publish simultaneously often both receive recognition (e g Buchwald-Hartwig reaction) and reactions discovered by one lab and developed or modified by another often bear two names (e g Johnson-Claisen rearrangement) Also as Drahl mentions in her article reaction names do change over time

Claisen rearrangement explained Claisen rearrangement should not be confused with Claisen condensation The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen The heating of an allyl vinyl ether will initiate a [3 3]-sigmatropic rearrangement to give a γ δ-unsaturated carbonyl

100 named reactions

31 curtius-rearrangement 87 This is used in Synthesis of Oseltamivir Angew Chem Int Ed 2009 48 1304 substrate product involves thermal decomposition of an acyl azide to an isocyanate with loss of nitrogen gas 32 williamson-ether-synthesis 95 This is used in Synthesis of Glycyrol Tetrahedron Lett 2008 49 6835 substrate product 33 henry-reaction 96 This is used in Total synthesis of

rearrangement Cope rearrangement Dess Martin oxidation Diels Alder cycloaddition enyne metathesis Friedel-Crafts acylation and alkylation Grignard reaction Heck reaction Johnson Claisen rearrangement Mannich reaction Mc Murry coupling Mitsnobu reaction Nazrov cyclisation Sharpless asymmetric epoxidation Shi asymmetric epoxidation Puasand Khand reaction Wittig reaction

General procedure for preparation of γ-unsaturated acids via Johnson-Claisen rearrangement and subsequent hydrolysis: A solution of appropriately substituted prop-2-en-1-ol (1 eq ) triethylorthoacetate (10 eq ) and cyclohexanoic acid (0 1 eq ) was heated at reflux for 3 h The reaction mixture was allowed to cool and the organic layer extracted with Et2O The organic layer was washed with

③ Sigmatropic rearrangement reaction (시그마결합 자리 옮김 반응) - Cope / Oxy-Cope / Aza-Cope rearrangement reaction - Claisen / Aza-Claisen rearrangement reaction - Ireland-Claisen rearrangement reaction - Johnson-Claisen rearrangement reaction - Eschenmoser-Claisen rearrangement reaction - Overman rearrangement reaction - Wittig rearrangement reaction 7 Rearrangement

Claisen also discovered other important 3 3 reactions including the Eschenmoser-Claisen Rearrangement and the Johnson-Claisen Rearrangement which use the reagents N N-dimenthylacetamide and triethylortoacetate respectively 1) Oxy-Cope Rearrangement: An additional subset of this rearrangement is the anion assisted Oxy-Cope rearrangement that results in a 10 10

General procedure for preparation of γ-unsaturated acids via Johnson-Claisen rearrangement and subsequent hydrolysis: A solution of appropriately substituted prop-2-en-1-ol (1 eq ) triethylorthoacetate (10 eq ) and cyclohexanoic acid (0 1 eq ) was heated at reflux for 3 h The reaction mixture was allowed to cool and the organic layer extracted with Et2O The organic layer was washed with

Johnson-Claisen rearrangement of Z-allylic alcohol 237 derived from diacetone-d-glucose 2 in 3 step reactions stereoselectively generated a quaternary carbon to give ester 238 as a single diastereomer (Scheme 21) The bicyclic structure of 237 completely controlled the facial selectivity of the sigmatropic rearrangement the C C bond formed from the less hindered β-face The rearranged

Intermediate 3 forms ester 5 by rearrangement (Johnson-Claisen) A C-O single bond is broken as a C-C single bond is formed while two double bonds move j) Use three curved arrows on structure 3 to illustrate this process [Note: One direction of arrow motion is preferable to the other Explain The stereochemistry of this rearrangement i e (E)- over (Z)- double bond has been explained

Table 4-Substrates and conditions attempted in Johnson-Claisen rearrangement 77 Table 5-Metabolism of halogen substituted benzoate esters by TDO 80 - Xll-List of Abbreviations 2 4DNP 2 4-dinitrophenyl hydrazine Ac acetyl Boc tert-butyloxycarbonyl (BochO di-tert-butyl dicarbonate Cbz carboxybenzyl CDCh deutero-chlorofornn CDCh chlorofornn conc concentrated CSA

General procedure for preparation of γ-unsaturated acids via Johnson-Claisen rearrangement and subsequent hydrolysis: A solution of appropriately substituted prop-2-en-1-ol (1 eq ) triethylorthoacetate (10 eq ) and cyclohexanoic acid (0 1 eq ) was heated at reflux for 3 h The reaction mixture was allowed to cool and the organic layer extracted with Et2O The organic layer was washed with

Johnson-Claisen Rearrangement Hoffmman Rearrangement PdCl2(dppf) OTIPS 9-BBN B OTIPS Suzuki-Miyaura coupling B OTIPS OH H H2N O AcO H MeC(OMe)3 +H(PivOH) ≡ Grubbs 1st TeocHN Boc N TIPSO propargyl bromide NaH TeocN Boc N TIPSO C TeocN Boc N TIPSO TMS H H D TeocN Boc N TIPSO TMS H H TeocN Boc N TIPSO H H H TMS TeocN Boc N TIPSO H H H E BF3•Et2O

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