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Design of novel titanium(IV) Schiff-...

Singer, Robert Alan.

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Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes./
Author:	Singer, Robert Alan.
Description:	182 p.
Notes:	Source: Dissertation Abstracts International, Volume: 58-01, Section: B, page: 0208.
Contained By:	Dissertation Abstracts International58-01B.
Subject:	Chemistry, Organic. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9720015
ISBN:	0591285479

Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes.
Singer, Robert Alan.

Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes. - 182 p.

Source: Dissertation Abstracts International, Volume: 58-01, Section: B, page: 0208.

Thesis (Ph.D.)--California Institute of Technology, 1997.

A novel chiral Schiff base ligand derived from 2-amino-2utylsalicylaldehyde has been prepared. When binding the chiral ligand to titanium (IV) with 3,5-di-

ISBN: 0591285479Subjects--Topical Terms:

516206
Chemistry, Organic.

Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes.
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020 $a 0591285479
035 $a (UnM)AAI9720015
035 $a AAI9720015
040 $a UnM $c UnM
100 1 $a Singer, Robert Alan. $3 1903238
245 1 0 $a Design of novel titanium(IV) Schiff-base complexes for catalytic, enantioselective aldol additions to aldehydes.
300 $a 182 p.
500 $a Source: Dissertation Abstracts International, Volume: 58-01, Section: B, page: 0208.
502 $a Thesis (Ph.D.)--California Institute of Technology, 1997.
520 $a A novel chiral Schiff base ligand derived from 2-amino-2 $\ sp\prime $- hydroxy-1,1 $\ sp\prime $- binaphthyl and 3-bromo-5- $\ sp{t} $b utylsalicylaldehyde has been prepared. When binding the chiral ligand to titanium (IV) with 3,5-di- $\ sp{t} $b utylsalicylic acid, the complex formed functions as an efficient catalyst for the Mukaiyama aldol addition reaction. Using only 1-2 mol% of the catalyst, silyl ketene acetal additions to aldehydes were carried out in good chemical yield and in excellent levels of enantioselectivity. Unsaturated aldehydes tended to produce adducts in 95-99% ee, while aliphatic aldehyde products were typically obtained in 94-95% ee.
520 $a The methodology was extended to include dienolate additions to aldehydes by utilizing silyl enol ethers of dioxinones. Optimal selectivities in the dienolate additions were obtained with unsaturated, unbranched aldehydes (90-94% ee). Aromatic and aliphatic aldehydes were usually isolated in 80-84% ee. Since many of the adducts were crystalline solids, the optical purity was enhanced by recrystallization. By heating the dioxinone adduct in the presence of an alcohol or amine, the products were transformed to more useful $\ beta $- ketoesters or $\ beta $- ketoamides.
520 $a To demonstrate the utility of the methodology developed, the asymmetric addition reactions have been applied to the total synthesis of (R)-epinephrine and macrolactin A. After carrying out an enantioselective acetate addition to 3,4-dimethoxybenzaldehyde in 95% ee, the $\ beta $- hydroxyester was converted to the amino-alcohol by a Hoffman rearrangement and a reduction. After deprotecting the catechol, (R)-epinephrine was obtained in 5 steps overall. Dienolate additions to $\ beta $- stannylpropenal were employed to prepare two key fragments of macrolactin A. The convergent route involved stitching together three fragments with a Stille coupling and a Horner-Emmons olefination. Macrocyclization was accomplished by an intramolecular Stille coupling.
590 $a School code: 0037.
650 4 $a Chemistry, Organic. $3 516206
650 4 $a Chemistry, Inorganic. $3 517253
690 $a 0490
690 $a 0488
710 2 0 $a California Institute of Technology. $3 726902
773 0 $t Dissertation Abstracts International $g 58-01B.
790 $a 0037
791 $a Ph.D.
792 $a 1997
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9720015