Following are the final steps in one industrial synthesis of vitamin A acetate. H,SO, ÓH (1) (2) (3) Pseudoionone B-Ionone (racemic) OH Br Ph P, HBr (4) (5) (racemic) OCCH3 Vitamin A acetate (a) Propose a mechanism for the acid-catalyzed cyclization in Step 1. (b) Propose reagents to bring about Step 2. (c) Propose a mechanism for formation of the phosphonium salt in Step 4. (d) Propose reagents to bring about Step 3. (e) Show how Step 5 can be completed by a Wittig reaction.
Following are the final steps in one industrial synthesis of vitamin A acetate. H,SO, ÓH (1) (2) (3) Pseudoionone B-Ionone (racemic) OH Br Ph P, HBr (4) (5) (racemic) OCCH3 Vitamin A acetate (a) Propose a mechanism for the acid-catalyzed cyclization in Step 1. (b) Propose reagents to bring about Step 2. (c) Propose a mechanism for formation of the phosphonium salt in Step 4. (d) Propose reagents to bring about Step 3. (e) Show how Step 5 can be completed by a Wittig reaction.
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
Chapter19: Enolate Anions And Enamines
Section: Chapter Questions
Problem 19.60P: Following is a retrosynthetic analysis for an intermediate in the industrial synthesis of vitamin A....
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![Following are the final steps in one industrial synthesis of vitamin A acetate.
H,SO,
ÓH
(1)
(2)
(3)
Pseudoionone
B-Ionone
(racemic)
OH
Br
Ph P, HBr
(4)
(5)
(racemic)
OCCH3
Vitamin A acetate
(a) Propose a mechanism for the acid-catalyzed cyclization in Step 1.
(b) Propose reagents to bring about Step 2.
(c) Propose a mechanism for formation of the phosphonium salt in Step 4.
(d) Propose reagents to bring about Step 3.
(e) Show how Step 5 can be completed by a Wittig reaction.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F87a42ae5-c820-4a8e-a772-eb6b3eb32e94%2F12abb33a-c134-4b0f-a128-7ebea4265984%2Fwtfxx5n.jpeg&w=3840&q=75)
Transcribed Image Text:Following are the final steps in one industrial synthesis of vitamin A acetate.
H,SO,
ÓH
(1)
(2)
(3)
Pseudoionone
B-Ionone
(racemic)
OH
Br
Ph P, HBr
(4)
(5)
(racemic)
OCCH3
Vitamin A acetate
(a) Propose a mechanism for the acid-catalyzed cyclization in Step 1.
(b) Propose reagents to bring about Step 2.
(c) Propose a mechanism for formation of the phosphonium salt in Step 4.
(d) Propose reagents to bring about Step 3.
(e) Show how Step 5 can be completed by a Wittig reaction.
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