Reagent-Controlled Regiodivergent Resolution of Unsymmetrical Oxabicyclic Alkenes Using a Cationic Rhodium Catalyst

Webster, Robert; Böing, Christian; Lautens, Mark

doi:10.1021/ja807942m

Cited by 115 publications

(49 citation statements)

References 22 publications

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“…What is less common is the possibility to get regioisomeric products deriving from different enantiomers of the starting material (regiodivergent kinetic resolution). [27][28][29][30][31][32] As expected, the chemical transformations performed on the enantiopure allylic substrates show a very strong catalyst control on the regioselectivity. It will be exemplified in Scheme 8, Scheme 9 and Scheme 10.…”

Section: Allylic Substitutionmentioning

confidence: 87%

“…The authors found that (R)-30 and (S)-30 gave different regioselectivities for a chiral ligand of a given configuration (see data in Scheme 11). For example (S)-i-PrPhox provided predominantly products Allylic substitution on some oxabicyclic systems 33 has been widely studied, especially by Lautens et al [32] Chiral rhodium complexes in methanol provided a regioselective cleavage according to the configuration of the diphosphine ligand 36 in the complex (Scheme 12). The isomeric alcohols formerly derived from the cleavage (a or b types) of the bridged oxygen, with endo attack of methanol on one or the other side of the double bond.…”

Section: Allylic Substitutionmentioning

confidence: 99%

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Regioselective Reactions on a Chiral Substrate Controlled by the Configuration of a Chiral Catalyst

Kumar

Kagan

2010

Adv Synth Catal

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A racemic mixture may be partially transformed in the presence of a chiral catalyst by kinetic resolution and formation of products with new structural features. If the starting material is fully consumed the products may still be enantiomerically enriched. The situation is summarized in the Introduction. A brief discussion on the regioselective transformations occurring on a racemic mixture under the influence of a chiral catalyst is presented in Section 2. Often stereo-differences occur, each enantiomer of the starting material resulting in a different product. It allows one to predict what the behaviour of some enantiopure substrates should be in presence of each of the enantiomers of a chiral catalyst. Many examples are presented in Section 3. The chiral substrates under consideration have two different reacting sites, usually of the same nature (OH, C=C, allylic positions, C À H for carbene insertion, epoxide fragment, etc.). In some cases the absolute configuration of the catalyst allows an excellent control of the regioselectivity. This approach is promising for the selective transformation of chiral molecules.

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Section: Allylic Substitutionmentioning

confidence: 87%

Section: Allylic Substitutionmentioning

confidence: 99%

Regioselective Reactions on a Chiral Substrate Controlled by the Configuration of a Chiral Catalyst

Kumar

Kagan

2010

Adv Synth Catal

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“…Despite the dominant role exerted by bridgehead substituted oxabicyclic alkene substrates in determining ring-opening regioselectivity, it was demonstrated that a chiral Rh I catalyst can override this bias (Scheme 10.24) [23] the absolute configuration of the chiral ligand when ring-opening enantioenriched oxabicyclic alkene 60 resulted in two different regiomeric products 61 and 62.…”

Section: Mechanistic Modelmentioning

confidence: 99%

CarbonHeteroatom Bond Formation by RhI‐Catalyzed Ring‐Opening Reactions

Fleming¹,

Lautens

2010

Catalyzed Carbon‐Heteroatom Bond Formation

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Transition metal-catalyzed allylic nucleophilic substitution (ANS) represents an important reaction for the construction of useful chiral building blocks. One class of ANS reactions is the transition metal-catalyzed ring-opening of strained bridged bicyclic allylic ethers and amines of general structure 1 by nucleophiles to give the corresponding cyclohexene adducts 2 (Scheme 10.1). As the leaving group remains within the product, this reaction allows the possibility of generating defined contiguous stereogenic centers within the product when starting from a meso-substrate and carrying out the reaction under asymmetric conditions.The majority of research focus has involved developing methodologies for the ring-opening of strained allylic ethers and amines of general structure 1 by carbon or hydride nucleophiles forming carbon-carbon or carbon-hydrogen bonds during the process. A number of research groups [1], including our own [2], have demonstrated that a variety of transition metal complexes can catalyze this reaction, and, depending on the combination of metal catalyst and nucleophile, different diastereoisomers of the product can be preferentially formed. However, less attention has been applied to the ring-opening of compounds of general structure 1 by heteroatom nucleophiles, which would form valuable carbon-heteroatom bonds. To date, Rh I -complexes have been the most extensively explored catalysts for this type of reaction. The first reported example was by Hogeveen and Middelkoop, who in 1973 demonstrated that [Rh(CO) 2 Cl] 2 could catalyze the ring-opening of 4 by MeOH to give one diastereoisomer of 5 (Scheme 10.2) [3]. It was later determined by Ashworth and Berchtold that the methoxy and hydroxy substituents have a cis-relationship by analysis of the coupling constant between H a and H b in the 1 H NMR spectrum of cycloadduct 6 [4]. While mechanistic details were not discussed, Brønsted acid catalysis seemed unlikely as reaction of 4 with protic catalysts resulted in the aromatized product 3.Since the seminal report by Hogeveen and Middelkoop, our group and others have examined the synthetic utility and mechanistic pathway of the Rh I -catalyzed ring-opening of strained bridged bicyclic allylic ethers and amines by heteroatom Catalyzed Carbon-Heteroatom Bond Formation. Edited

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“…In the past decades, the group of Lautens and others reported rhodium-catalyzed asymmetric ring-opening of oxabenzonorbornadiene with a wide range of nucleophiles including thiols [10], phenols [11], organoboronic acids [12–13], dialkylzincs [14–15], carboxylates [16], sulfur nucleophiles [17], and various amines [18–19]. …”

Section: Introductionmentioning

confidence: 99%

Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles

Yang

Hu²,

Long³

et al. 2009

Beilstein J. Org. Chem.

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SummaryIridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with various aliphatic and aromatic secondary amines are reported for the first time. The reaction gave the corresponding trans-1,2-dihydronaphthalenol derivatives in good yields with moderate enantioselectivities in the presence of 2.5 mol % [Ir(COD)Cl]2 and 5 mol % bisphosphine ligand (S)-p-Tol-BINAP. The trans-configuration of 3f was confirmed by X-ray crystallography.

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Reagent-Controlled Regiodivergent Resolution of Unsymmetrical Oxabicyclic Alkenes Using a Cationic Rhodium Catalyst

Cited by 115 publications

References 22 publications

Regioselective Reactions on a Chiral Substrate Controlled by the Configuration of a Chiral Catalyst

Regioselective Reactions on a Chiral Substrate Controlled by the Configuration of a Chiral Catalyst

CarbonHeteroatom Bond Formation by RhI‐Catalyzed Ring‐Opening Reactions

Iridium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes with secondary amine nucleophiles

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