(c) With reference to the following reaction scheme: Me Mé N Boc 20 OMe DIBAL, toluene, -78 °C then H30Ⓡ w/up Me- Mé N Boc 21 H Useful structure: DIBAL= H. AI (i) Provide a curved arrow mechanism for the reduction of ester 20 to aldehyde 21. (ii) Explain why the reduction of ester 20 selectively affords aldehyde 21 in the of DIBAL, whereas treatment of 20 with LiAlH4 leads to over-reduction. presence

(c) With reference to the following reaction scheme: Me Mé N Boc 20 OMe DIBAL, toluene, -78 °C then H30Ⓡ w/up Me- Mé N Boc 21 H Useful structure: DIBAL= H. AI (i) Provide a curved arrow mechanism for the reduction of ester 20 to aldehyde 21. (ii) Explain why the reduction of ester 20 selectively affords aldehyde 21 in the of DIBAL, whereas treatment of 20 with LiAlH4 leads to over-reduction. presence

Organic Chemistry

8th Edition

ISBN:9781305580350

Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Publisher:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. Foote

Chapter11: Ethers, Epoxides, And Sulfides

Section: Chapter Questions

Problem 11.24P: The following equation shows the reaction of trans-2,3-diphenyloxirane with hydrogen chloride in...

See similar textbooks

Similar questions

Jut L Br HNO3/H₂SO4 NaOEt M N K (i) Give the structure of M and a mechanism for its formation. L and of bromoquinoline Explain the reactivity regioselectivity of the reaction. (ii) Give the structure of N and a mechanism for its formation. and bromoquinoline L Explain the reactivity of regioselectivity of the reaction.
Identify the following compound from its IR and proton NMR spectra. C,H1,0: 'H NMR 8 3.31 (3H, s); 8 2.41 (1H, s); & 1.43 (6H, s) IR: 2110, 3300 cm- (sharp)
21.3 Provide the reagents. -ОН CI
(c) Treating lactone B with two equivalents of phenylmagnesium bromide, followed by hydrolysis in aqueous acid, gives a compound with the molecular formula C18H22O2, as shown below. Propose a structural formula for this compound. 1. PhMgBr (2 eq.) 2. H'/H>O C18H2202 bj 1o 14 10I f6 40 & 3 4 00 (8)
18.26 Predict the products of the following ether cleavage reactions: LOCH CH3 OC(CH3)3 (a) HI CF3CO,H, ? (b) H2O HI HI (c) Н,С— СНОСH,CH, (d) (CH3);CCH,OCH,CH3 H20 H2O
CH3 NH3, H* H3C H3C CH: Substituted pyrroles are often prepared by treatment of a 1,4-diketone with ammonia in the presence of catalytic H*. The mechanism involves the following steps: 1) Protonation of the carbonyl oxygen and nucleophilic attack by ammonia form tetrahedral intermediate 1; 2) Proton transfer leads to protonated carbinolamine 2; 3) B-elimination leads to enamine 3; 4) Protonation of the carbonyl oxygen and nucleophilic attack by the amine form tetrahedral intermediate 4; 5) Proton transfer leads to protonated carbinolamine 5; 6) B-elimination leads to the final product. Write out the reaction mechanism on a separate sheet of paper, and then draw the structure of tetrahedral intermediate 4. • You do not have to consider stereochemistry. You do not have to explicitly draw H atoms. Do not include lone pairs in your answer. ZI
Q.5 a) Draw the structures and specify the stereochemistry of compounds A-C. Pyridine i) LIAIH, в NaNg -SO̟CI (S-Octan-2-ol A MEOH i) H20 b) Outline a synthesis of the following bio-relevant compound using reagents with two or less carbon atoms. N(CH3)3 c) Suggest a mechanism for the following reactions. н. он OH POH i) H20 HO H30 ii) -CO2H OH The End
The following equation shows the reaction of trans-2,3-diphenyloxirane with hydrogen chloride in benzene to form 2-chloro-1,2-diphenylethanol. (a) How many stereoisomers are possible for 2-chloro-1,2-diphenylethanol? (b) Given that opening of the epoxide ring in this reaction is stereoselective, predict which of the possible stereoisomers of 2-chloro-1,2-diphenylethanol is/are formed in the reaction.
As far back as the 16th century, South American Incas chewed the leaves of the coca bush, Erythroxylon coca, to combat fatigue. Chemical studies of Erythroxylon coca by Friedrich WĂ¶hler in 1862 resulted in the discovery of cocaine, C17H21NO4, as the active component. Basic hydrolysis of cocaine leads to methanol, benzoic acid, and another compound called ecgonine, C9H15NO3. Oxidation of ecgonine with CrO3 yields a keto acid that readily loses CO2 on heating, giving tropinone. (a) What is a likely structure for the keto acid? (b) What is a likely structure for ecgonine, neglecting stereochemistry? (c) What is a likely structure for cocaine, neglecting stereochemistry?
The key step in a reported laboratory synthesis of sativene, a hydrocarbon isolated from the mold Helminthosporium sativum, involves the following base treatment of a keto tosylate. What kind of reaction is occurring? How would you complete the synthesis?
Devise a synthesis of (E)-tetradec-11-enal, a sex pheromone of thespruce budworm, a pest that destroys fir and spruce forests, fromacetylene, Br(CH2)10OH, and any needed organic compounds orinorganic reagents.
ArCN MeMgl Et₂O/C6H6 HN Ar NaBH3CN, AcOH H₂N Ar 8 6 Scheme 4: Preparation of [(9-anthryl)alkyl]- and (mesitylalkyl)amines 6h and 6j from nitriles via imines 8.