assignment3answers - CHM 3120 Assignment 3 Answers 1. Show...

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1 CHM 3120 Assignment 3 Answers 1. Show the product of the following reactions. Draw intermediates to explain the observed stereochemistry: Ph O Et SMe Ph O Et SMe H O Et N EtMgBr TBDPSO CHO OTBS N OLi O O a) LiBH(sBu) 3 b) c) d) + Zn(BH 4 ) 2 LiBH(sBu) 3 Et SMe Ph O SMe HE t O Ph SMe t Ph O SMe t H Ph HO SMe t H OH Ph Et SMe Ph OH Et SMe Ph OH favored disfavored a) anti syn major BH(sBu) 3 BH(sBu) 3 Et SMe Ph O Zn(BH 4 ) 2 Et SH Ph O Zn Me Et MeS H H Ph ZnO H 3 O+ Et SMe Ph OH b) BH 4 Et N H O EtMgBr Et NH H O Mg Et H Et H MgO H 3 O+ Et N Et OH c) Et- N
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2 R Me H O R Me H O H R Me H H O R Me H H LiO R Me H OLi H R Me OH favored disfavored d) anti syn major TBDPSO CHO OTBS N OLi O O R N OLi O O N OLi O O N OLi O O N O O O N O O O N O O O H 3 O+ R Me OH N O O O TBDPSO TBSO OH N O O O Major Product Syn 2. Consider the following reaction: O Me O Me Ph OH 1) LDA 2) PhCHO a) What is the major enolate formed? OLi b) Explain why this is the major enolate. O LDA OLi - kinetic conditions less substituted enolate OLi E enolate disfavored by steric interaction c) Show the reaction pathways leading to the two diasteriomers formed.
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3 OO Li H Ph Cy Me H Li R H Cy Me H Li R H Cy Me H Li H Ph Cy Me H Ph OH Me O R OH Me O favored Major Interaction Disfavored Syn Anti O- d) What is the stereochemistry of the major product (syn or anti)? Indicate on your reaction pathway the unfavorable interaction.
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assignment3answers - CHM 3120 Assignment 3 Answers 1. Show...

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