Feb_03 - The Diels-Alder Reaction heat heat How How does this reaction occur 6 sp2 carbons carbons heat carbons 2 sp2 carbons 4 sp3 carbons carbons

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 2/4/2010 The Diels-Alder Reaction + heat heat How How does this reaction occur? 6 sp2 carbons carbons + heat carbons 2 sp2 carbons 4 sp3 carbons carbons On a piece of paper sketch the product of the following DielsAlder reaction. + energy A. B. C. D. 1 progress of reaction 2 How does this reaction occur? 6 sp2 carbons carbons + heat carbons 2 sp2 carbons carbons 4 sp3 carbons Which MO interactions the reactants are involved in this reaction? heat + + energy progress of reaction energy 3 progress of reaction 4 Which MO interactions the reactants are involved in this reaction? Ψ4 LUMOene Ψ3 Ψ* In addition to Ψ2 and Ψ* which other MOs of the reactants are and involved in this reaction? Ψ4 LUMOene Ψ3 LUMOdiene Ψ* Ψ2 HOMOdiene Ψ Ψ2 HOMOdiene HOMOene Ψ stabilization Ψ1 Ψ1 and (A) Ψ1 and Ψ (B) Ψ1 and Ψ* and (C) Ψ2 and Ψ* and (D) Ψ2 and Ψ and 5 (A) Ψ3 and Ψ and (B) Ψ4 and Ψ* and (C) Ψ3 and Ψ* and (D) Ψ2 and Ψ and 6 1 2/4/2010 Which MO interactions the reactants are involved in this reaction? Ψ4 LUMOene Ψ3 LUMOdiene What is the product of the following Diels-Alder Reaction? Diels- stabilization + concerted reaction Ψ2 HOMOdiene HOMOene no stabilization O + CH3 H Ψ1 H O CH3 O CH3 H O H H O H 7 AH CH3 B CH3 C H CH3 D H CH3 8 Why is this the major product of this reaction? What reactants would give the cis stereoisomer? cis + + The cis principle O + CH3 H H H O H CH3 The cis principle O H H CH3 O H CH3 trans + trans trans O H H O H CH3 9 H H O H CH3 10 + cis H CH3 H What is the major product of the following Diels-Alder reaction? Diels- What is the major product of the following Diels-Alder reaction? DielsCO2CH3 CH3 CO2CH3 CO2CH3 CH3 CO2CH3 CO2CH3 CH3 H 3C H 3C CO2CH3 CO2CH3 H 3C H 3C + A CH3 + CO2CH3 c c t c t t 11 B CH3 + CO2CH3 CH3 C CH3 D CO2CH3 CO2CH3 CO2CH3 CO2CH3 CH3 CH3 t c t c CH3 c t CO2CH3 12 2 2/4/2010 What is the major product of the following Diels-Alder reaction? DielsCO2CH3 H 3C H 3C CO2CH3 CO2CH3 H 3C H 3C CH3 CO2CH3 CO2CH3 CH3 CO2CH3 CO2CH3 CH3 What is the major product of the following Diels-Alder reaction? DielsCO2CH3 H 3C H 3C CO2CH3 CO2CH3 H 3C H 3C CH3 CO2CH3 CO2CH3 CH3 CO2CH3 CO2CH3 CH3 A CH3 + B CO2CH3 CH3 C D A CH3 + B CO2CH3 CH3 C CH3 D CO2CH3 CO2CH3 CO2CH3 CO2CH3 CH3 H CH3 CH3 H3C H3CO2C CO2CH3 14 CH3 CH3 H3C H3CO2C CO2CH3 CO2CH3 H CH3 H3C H3CO2C CO2CH3 H3C H3CO2C H CH3 CO2CH3 13 CH3 CH3 H3C H3CO2C CO2CH3 CO2CH3 H H3C H3CO2C CO2CH3 The cis principle predicts the relative stereochemistry of the substituents on the diene and dienophile. cis? OCH3 + H3C CH3 CH3 O CH3 OCH3 O CH3 CH3 CH3 Which of the two diastereomers is the product of the DielsDielsAlder reaction? trans? OCH3O OCH3 CH3 CH3 + O CH3 OCH3 O CH3 OCH3O CH3 or A B Which would you predict to be the major product of the above reaction. 15 16 Which of the two diastereomers is the product of the DielsDielsAlder reaction? OCH3 H CH3 H OCH3 Which of the following transition states would you predict to be more stable? OCH3 H H OCH3 OCH3 O CH3 H H H O OCH3 + O O OCH3 O O OCH3O CH3 OCH3 OCH3 + O O CH3 OCH3 H H CH3 CH3 CH3 A endo H OCH3 H OCH3 OCH3O CH3 O H H O H O B exo Alder endo rule: 17 H O The endo reaction pathway is more favorable than exo. exo. 18 3 2/4/2010 The cis principle and the Alder endo rule address relative cis endo stereochemical possibilities of the product. The question of regiochemistry needs to be addressed. O + CH3 OCH3 O CH3 Which is the major product of the following Diels-Alder reaction? + OCH3 OCH3 + O CH3 OCH3 O CH3 A OCH3 + OCH3 CH3 O CH3 B O 20 19 OCH3 O CH3 What is the product of the following Diels-Alder reaction? Diels- OCH3 + O CH3 OCH3 O CH3 OCH3 + O CH3 OCH O OCH3 O 3 CH CH3 3 A OCH3 + OCH3 CH3 O CH3 B O 21 energy progress of reaction 22 Reactivity of dienes and dienophiles. dienophiles. Which of the following reactions should go faster? Reactivity of dienes and dienophiles. dienophiles. Which of the following reactions should go faster? A + A B + B 23 24 4 2/4/2010 Which diene and dienophile would give the following cyclohexene? + OCH3 H heat LUMO LUMO OCH3 O O O O O H H H H energy (A) (B) O H (C ) O H ( D) HOMO OCH3 H HOMO O OCH3 electron donating groups on the diene enhance its reactivity Why do electron withdrawing groups on the dieneophile enhance its reactivity? 25 26 Which diene and dienophile would give the following cyclohexene? + heat Which stereoisomer is the major product? + heat O H O O H O H H H H O (A) (B) O H (C ) O H ( D) O + H H major product! O O endo A enantiomers or H diastereomers? sterochemistry? O H O 27 H exo B 28 Is it possible to control the reaction conditions so that one of these enantiomers is the major product? + heat Is it possible to control the reaction conditions so that one of these enantiomers is the major product? + heat TfO TfO N H a lewis acid lewis B Ar H N Lewis acids catalyze the DielsDiels-Alder reaction. Why? Why? O H H O H + H O H B Ar O + H H H O + H H + O enantiomers 29 enantiomers 30 5 2/4/2010 Is it possible to control the reaction conditions so that one of these enantiomers is the major product? + heat TfO H Ar Ar B Ar N H chiral lewis acid catalysts can give one enantiomer as the the major product. H H H O + H O H O + major product! enantiomers 31 32 6 ...
View Full Document

This note was uploaded on 04/06/2010 for the course CHE 326 taught by Professor Fowler during the Spring '08 term at SUNY Stony Brook.

Ask a homework question - tutors are online