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NOCHOMeMeGdelavatine A![]()
NCHOMeMeGdelavatine A![]()
OMeBrBr![]()
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MeBrHOOEtO![]()
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MeBrHOOEtO![]()
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BAEOSOOFFFOTfOOCO2EtMeOMeSnMe3SnOCHOMeB(Pin)OOCO2EtMeOBrBrOCOOOOCO2EtMeOCHOMeOOCO2MeOOCO2EtMeOCHOMeNCNFGDDOOCO2EtMeMeMeOMeBrBrOMeBr![]()
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OMeMeMeBrHOMeOMeMeMeBrHOOCO2EtMeMeMeHXYYOKt-BuOKSOOCuNClNSOOFFFSOOFFFNTf2A Short Synthesis of Delavatine A Unveils New Insights into Site-
Selective Cross-Coupling of 3,5-Dibromo-2-pyrone
Palani, V.; Hugelshofer, C. L.; Kevlishvili, L.; Liu, P.; Sarpong, R.
J. Am. Chem. Soc. 2019, 141, 2652−2660.1-49,106-851112-151) Br2
2) EtONa
3) O3
4) LDA, Tf2O5) Pd(dppf)Cl2, B2pin2
6) (Me3Sn)2CuLi
7) Dibal-H
8) TPAP, NMO9) Pd(PPh3)4, CuI, B
10) Pd(PPh3)4, CuTC, C11) NaCN, then K2CO3, MeI12) TBSOTf, Et3N,
then DBU, PhMe, D
13) LiAlH4
14) (COCl)2, DMSO, Et3N
15) NH4OAc,2) Show the mechanism of step 2.
hint: A cyclopentane is formed5) Which by-product must be avoided ?
Suzuki-coupling between vinyl triflate
and vinyl-boronate9) Give the name of steps 9 and 10
Suzuki-Cross-Coupling
10) Show the structure of CuTC11) Show the mechanism of step 11
1,6-addition followed by a
vinylogous retro-oxa-Michael
12) Show the mechanism of step 126) Propose two mechanisms
Michael-retro-Michael or
1,4-addtion followed by an E1cB or Oxidative addition-Reductive Elimination++Extra questions: Step 2The relationship between oxyallyl cation and cyclopropanone
is an equilibrium or a ressonance? answer: equilibrium
It is an electrocyclization.
Conrotatory or disrotatory? Disrotatory
I want you to show me the mechanism of two reactions:
- an oxyallyl cation with an nucleophile;
Nucleophilic addition followed by enolate protonation
- with a diene: 4+3 cycloadditionExplain the mechanistical difference between E1cB and a E2 ?For Y = EDG or weak EWG: E2 Mechanism
(Me, MeO or Cl)
For Y = strong EWG: E1cB (CN or NO2)Why is there a typical 1,4 vs 1,2 selectivity for organocuprates?Consider the elimination of a homobenzyl halide in the presence of a baseCan you show two reagents to replace Tf2O? PhNTf2 and CominsHow to avoid the Suzuki? Avoid addition of base (doule check)Mention that in a Hammett-Plot this is a classical example
of shift in inclination typical of shift in reaction mechanismWhat kind of selectivity is operating in step 9? regioselectivityWhat is the synthetic advantage of preparing two building
blocks from the same synthetcic intermediate?
There is an overrall reduction in the number of stepsWhat is the role of DBU?
To eliminate the cyano after the electrocyclizationExtra questions: Step 6Extra question: Step 4Extra question: Step 5Cu-coordinates to the double bond h-2 complex, migratory insertion then reductive eliminationE2 is concerted whereas E1cB is stepwise, in which initially there is a conjugated base formation
prior to the elimination of the leaving groupExtra questions: Step 9Extra questions: Step 10Extra questions: Step 12Show the mechanism of step 15Extra questions: Step 152p-electrocyclization![]()
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