Lecture4: 123.702
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Lecture4: 123.702

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Use of stoichiometric amounts of a chiral source. The usual suspects will be discussed, including borane reagents (mostly pinene derivatives) and the Brown allylation.

Use of stoichiometric amounts of a chiral source. The usual suspects will be discussed, including borane reagents (mostly pinene derivatives) and the Brown allylation.

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Lecture4: 123.702 Lecture4: 123.702 Presentation Transcript

  • LECTURE FOUR chiral reagents gareth j rowlands
  • O (R)-muscon e J. Chem. Soc., Chem., Commun., 1990, 795 & J. Chem. Soc., Perkin Trans. 1, 1991, 1445 ©baboon™@flickr
  • how O is the selectivity achieved? NH OH N H (2 eq.) MeLi, CuI O 99% ee
  • chiral reagent control substrate (achiral) chiral reagent [ ] substrate (achiral) chiral reagent chiral product
  • problem it is wasteful ©maol@flickr
  • H O B (+)-α-pinene 9-BBN•THF of synthesis chiral H B reagent alpine borane
  • O RL RS H B O B H RL RS with a reduction H OH chiral RL RS reagent
  • O RL RS H B O B H RL RS with a reduction H OH chiral RL RS reagent
  • O RL RS H B O B H RL RS with a reduction H OH chiral RL RS reagent
  • (R)-fluoxetin e Prozac J. Org. Chem., 1986, 51, 3394 & J. Am. Chem. Soc., 1988, 110, 1539 CF3 O H Me N H•HCl ©Touchstone Pictures
  • O Cl Cl Ipc B O H Ph H BCl Cl 2 (+)-Ipc2BCl H OH synthesis CF 3 Cl using a chiral O H Me N reagent H•HCl ≥99% ee 1 recrystallisation
  • of synthesis reagent chiral pinene
  • of synthesis reagent chiral (+)-α-pinene BH3 H H 1. TMEDA H 2. BF3•OEt2 B BH2 H H H H (–)-Ipc2BH (+)-IpcBH2
  • of use boron reagents chiral H H ii. H2O2 H OH H NaOH H H H B 98.4% ee H H H
  • of use boron reagents chiral Me Me ii. H2O2 H H NaOH H HO BH2 H 66% ee H
  • of use boron reagents chiral i. (–)-Ipc2BOTf iPr2NEt OH O O ii. RCHO R
  • ©Brittany G@flickr
  • enolate geometry i. (–)-Ipc2BOTf O iPr2NEt B O 2
  • reagent chiral B O control 2 H O H OH R H B O or H O OH O R R
  • OH O H O Me OH O O H H O Me (–)-laulimali de fijianolide B Org. Lett., 2001, 3, 3149 ©luxpacis@flickr
  • chiral reagent control OH O H O OH O O H H O (+)-Ipc2BO CO2Me OTBS H H H O O O OH OPMB CO2Me H H OTBS O H H O 86% O OPMB 62%de
  • organobora nes ©Pierre J.@flickr
  • allylation with organoboranes O L L R B O RZ RZ L R B RE RE L L L OH H2O2 B NaOH O R RZ RE R RZ RE
  • stereospecific O L L R B O RZ RZ L R B RE RE L L L OH H2O2 B NaOH O R RZ RE R RZ RE
  • stereospecific H L H L R H B B L vs L RE RE O O H R RZ RZ
  • stereospecific H L H L R H B B L vs L RE RE O O H R RZ RZ
  • stereospecific H L H L R H B B L vs L RE RE O O H R RZ RZ H OH H R RE OH RZ RE R RZ
  • synthesis BH3•SMe2 BOMe MeOH 2 MgBr K BF3•OEt2 B B 2 2
  • chiral reagent control OH B O Et Et H 2 92% ee
  • chiral reagent control OH B O Et Et H 2 92% ee H H H B OH Et H O Et
  • chiral reagent control CO2iPr OH O O t-Bu B CO2iPr t-Bu H O 82% ee
  • chiral reagent control CO2iPr OH O O t-Bu B CO2iPr t-Bu H O 82% ee H2O2 NaOH CO2iPr CO2iPr O O H CO2iPr H CO2iPr B B O O O O t-Bu t-Bu H H
  • OH O O O OH CO2H O O NaO2C OH O O O HO (+)-SCH351448 Org. Lett., 2005, 7, 3809 ©Exothermic@flickr
  • chiral reagent control O O O OH OH CO2H O O NaO2C OH O O O HO OBn O BnO2C O H OBn OH DCM, 0°C Ar BnO2C 80% O N 95% d.e. Si N Cl Ar