Cp<sub>2</sub>TiCl-Mediated Selective Reduction of α,β-Epoxy Ketones

Hardouin, Christophe; Chevallier, Floris; Rousseau, Bernard; Doris, Eric

doi:10.1021/jo001358g

Cited by 66 publications

(39 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, photoreduction may play an important role as well. As an example, the regioselective reductive opening of the threemembered ring in the ketoepoxide shown in Scheme 4 can be carried out by using a strongly reducing agent, such as in situ prepared Ti III [27] or sodium hydrogen telluride [28]. However, the same process can be carried out under mild conditions provided that the reaction occurs via the excited state, much easier to reduce than the corresponding ground state.…”

Section: Reductionmentioning

confidence: 99%

Photochemistry in synthesis: Where, when, and why

Protti

Dondi

Fagnoni

et al. 2007

Pure and Applied Chemistry

View full text Add to dashboard Cite

A series of photochemical reactions are assessed under the environmental aspect by using Eissen and Metzger's EATOS (environmental assessment tool for organic syntheses) method and are compared with strictly analogous thermal processes. These include C-C bond-forming reactions (arylation and alkylation) and selective oxidation and reduction reactions. In most cases, the photochemical method is experimentally simpler and less expensive than the thermal alternative. A disadvantage is that photochemical reactions are carried out in rather dilute solution, and this factor gives by far the main contribution to the assessment. However, if the solvent is recovered, the photochemical reaction is more environmentfriendly.

show abstract

Section: Reductionmentioning

confidence: 99%

Photochemistry in synthesis: Where, when, and why

Protti

Dondi

Fagnoni

et al. 2007

Pure and Applied Chemistry

View full text Add to dashboard Cite

show abstract

“…[16] In this manner bhydroxy ketones can be obtained in high yield. The synthesis of enantiomerically pure compounds is easily realised.…”

Section: Stoichiometric Opening Of Epoxides Via Electron Transfermentioning

confidence: 99%

“…[16] Thus, the relatively sensitive b-hydroxy ketones are also readily tolerated under the catalytic conditions.…”

Section: Reviewsmentioning

confidence: 99%

Titanocene-Catalysed Electron Transfer-Mediated Opening of Epoxides

Gansäuer

Narayan

2002

Advanced Synthesis & Catalysis

View full text Add to dashboard Cite

The use of epoxides as substrates for radical reactions via electron transfer is described. The discussion of the evolution of stoichiometric reagents focuses on recent developments in the field of titanocene(III) reagents. Special attention is devoted to the emergence of catalytic conditions for this useful procedure that has led to the discovery of reagent‐controlled radical reactions by variations of the cyclopentadienyl ligands.

show abstract

“…[161][162][163] There are no reports, however, of regioselective epoxide-opening reactions of a,b-epoxy amides, 164,165) in contrast to the success with a,b-epoxy ketones. [166][167][168][169][170][171][172] To realize highly regioselective epoxide-opening reactions of a,bepoxy amides, it is important to control the relative reactivity of the a-and b-positions. a,b-Epoxy amides have completely different reactivity depending on the b-substituents.…”

Section: Catalytic Asymmetric Epoxidation 3-1 Catalytic Asymmetric Ementioning

confidence: 99%

“…(2) The higher reactivity of the b-position of b-aryl a,b-epoxy amides 100, however, makes it difficult to obtain b-hydroxy amides 103 through C a -O bond cleavage (path B). Indeed, general conditions for selective C b -O bond cleavage of a,b-epoxy ketones, such as SmI 2 and Cp 2 TiCl 2 -Zn, [166][167][168][169][170][171][172] produced unsatisfactory results (trace amounts) with a,b-unsaturated and saturated amides as major products. To overcome this difficulty, we examined the so-called intramolecular hydride transfer using RedAl, 163,[173][174][175] which might react with N-H first to produce N-Al species 102 and the remaining hydride attacks the aposition of the epoxy amide.…”

Section: Catalytic Asymmetric Epoxidation 3-1 Catalytic Asymmetric Ementioning

confidence: 99%

Enantioselective Total Syntheses of Several Bioactive Natural Products Based on the Development of Practical Asymmetric Catalysis

Ohshima

2004

CHEMICAL & PHARMACEUTICAL BULLETIN

View full text Add to dashboard Cite

I present herewith enantioselective total syntheses of several bioactive natural products, such as (؊)-strychnine, (؉)-decursin, (؊)-cryptocaryolone diacetate, (؊)-fluoxetine, and aeruginosin 298-A, based on practical asymmetric catalyses (Michael reaction, epoxidation, and phase-transfer reaction) that I developed with coworkers in Prof. Shibasaki's group over the past 5 years. In the first part of this review, I discuss the great improvement of catalyst efficiency in an ALB-catalyzed asymmetric Michael reaction of malonate and application to the pre-manufacturing scale (greater than kilogram scale) and enantioselective total synthesis of (؊)-strychnine with the development of novel domino cyclization. To broaden the substrate generality of the Michael reaction, we developed a highly stable, storable, and reusable La-O-linked-BINOL complex. Further extension of the reaction using b b-keto ester as a Michael donor was achieved with the development of a La-NR-linked-BINOL complex, thereby improving indole alkaloid syntheses. In the second section, I discuss enantioselective total synthesis of (؉)-decursin using catalytic asymmetric epoxidation. To achieve the synthesis, we developed a new La-BINOL-Ph 3 As‫؍‬O (1 : 1 : 1) complex catalyst system, which has much higher reactivity and broader substrate generality than the previously developed catalyst systems. This allowed us to achieve catalytic asymmetric epoxidation of a a,b b-unsaturated carboxylic acid derivatives with high enantioselectivity and broad substrate generality for the first time by changing the lanthanide metal and reaction conditions. Among them, catalytic asymmetric epoxidation of a a,b b-unsaturated morpholinyl amides is quite useful in terms of synthetic utility of the corresponding a a,b b-epoxy morpholinyl amides. Highly catalyst-controlled enantio-or diastereoselective epoxidation of the a a,b b-unsaturated morpholinyl amides, coupled with diastereoselective reduction of b b-hydroxy ketones, enabled the synthesis of all possible stereoisomers of 1,3-polyol arrays with successful enantioselective total synthesis of several 1,3-polyol natural products, such as (؊)-cryptocaryolone diacetate. In addition, the development of a new regioselective epoxide-opening reaction of a a,b b-epoxy amides to the corresponding a a-and b b-hydroxy amides enhanced the usefulness of the present epoxidation and was applied to the enantioselective total synthesis of (؊)-fluoxetine. In the final section, I report the development of a new asymmetric two-center organocatalyst (TaDiAS) and its application to the enantioselective synthesis of aeruginosin 298-A and its analogues. Because of the remarkable structural diversity of TaDiAS, a practical asymmetric phase-transfer reaction with broad substrate generality was achieved. As a result, we succeeded in developing a highly versatile synthetic method for aeruginosin 298-A and its analogues. Inhibitory activity studies of the compounds against the serine protease trypsin provided preliminary information about their str...

show abstract

Cp₂TiCl-Mediated Selective Reduction of α,β-Epoxy Ketones

Cited by 66 publications

References 19 publications

Photochemistry in synthesis: Where, when, and why

Photochemistry in synthesis: Where, when, and why

Titanocene-Catalysed Electron Transfer-Mediated Opening of Epoxides

Enantioselective Total Syntheses of Several Bioactive Natural Products Based on the Development of Practical Asymmetric Catalysis

Contact Info

Product

Resources

About

Cp2TiCl-Mediated Selective Reduction of α,β-Epoxy Ketones

Cited by 66 publications

References 19 publications

Photochemistry in synthesis: Where, when, and why

Photochemistry in synthesis: Where, when, and why

Titanocene-Catalysed Electron Transfer-Mediated Opening of Epoxides

Enantioselective Total Syntheses of Several Bioactive Natural Products Based on the Development of Practical Asymmetric Catalysis

Contact Info

Product

Resources

About

Cp₂TiCl-Mediated Selective Reduction of α,β-Epoxy Ketones