0000000001303460
AUTHOR
Elsa Rodríguez
Recent Developments in the Chiral Brønsted Acid-catalyzed Allylboration Reaction with Polyfunctionalized Substrates
Asymmetric allylboration has played a central role in organic synthesis ever since the pioneering work by Hoffman and Brown, having found applications in the total synthesis of many natural products. A new dawn for this 40 year-old reaction occurred with the beginning of the new century when the first catalytic asymmetric methods came into play. In less than one decade, several methodologies, able to achieve the desired homoallylic alcohols with ee ranges in the high 90s, were developed. Among them, in the present account, we will disclose our contribution to the development of the chiral binolphosphoric-derived BrOnsted acid-catalyzed allylboration of aldehydes originally reported by Antil…
ChemInform Abstract: Asymmetric Allylation/Ring Closing Metathesis: One-Pot Synthesis of Benzo-Fused Cyclic Homoallylic Amines. Application to the Formal Synthesis of Sertraline Derivatives.
A stepwise process consisting of asymmetric allylation of imines of type (I) and following ring-closing metathesis of the resulting dienes (III) is developed to synthesize cyclic homoallylic amines.
ChemInform Abstract: Intramolecular Michael Reaction of tert-Butylsulfinyl Ketimines: Asymmetric Synthesis of 3-Substituted Indanones.
The reaction proceeds in the presence of the Ruppert—Prakash reagent (Tms-CF3) with either TBAT or TBAF as a base.
Base-Dependent Stereodivergent Intramolecular Aza-Michael Reaction: Asymmetric Synthesis of 1,3-Disubstituted Isoindolines
The nucleophilic addition (A(N)) / intramolecular aza-Michael reaction (IMAMR) process on Ellman's tert-butylsulfinyl imines, bearing a Michael acceptor in the ortho position, is studied. This reaction affords 1,3-disubstituted isoindolines with a wide range of substituents in good yields and diastereoselectivities. Interestingly, careful choice of the base for the aza-Michael step allows either the cis or the trans diastereoisomers to be exclusively obtained. This stereodivergent cyclization has enabled the synthesis of C2-symmetric bisacetate-substituted isoindolines. In addition, bisacetate isoindolines bearing two well-differentiated ester moieties are also noteworthy because they may a…
ChemInform Abstract: Tandem Nucleophilic Addition-Intramolecular Aza-Michael Reaction: Facile Synthesis of Chiral Fluorinated Isoindolines.
A highly stereoselective synthesis of fluorinated 1,3-disubstituted isoindolines is described. To this end, a tandem reaction consisting of a diastereoselective addition of fluorinated nucleophiles to Ellman’s N-(tert-butanesulfinyl)imines followed by an intramolecular aza-Michael reaction has been developed. This strategy allows for the construction of isoindolines bearing several degrees of fluorination (mono-, di-, or trifluoromethyl as well as heavier fluorinated groups). In the majority of all cases, the products are formed as single isomers.
γ-Silylboronates in the chiral Brønsted acid-catalysed allylboration of aldehydes.
The use of functionalised allylboronic esters in the catalytic enantioselective allylboration of aldehydes is described for the first time. γ-Silylallyl pinacolate derivatives give rise to α-silyl homoallylic alcohols in high yields, with complete diastereoselectivities and high enantioselectivities, in most of the cases. The usefulness of such intermediates is showcased by their transformation into fluorinated allylic alcohols.
Tandem Nucleophilic Addition−Intramolecular Aza-Michael Reaction: Facile Synthesis of Chiral Fluorinated Isoindolines
A highly stereoselective synthesis of fluorinated 1,3-disubstituted isoindolines is described. To this end, a tandem reaction consisting of a diastereoselective addition of fluorinated nucleophiles to Ellman's N-(tert-butanesulfinyl)imines followed by an intramolecular aza-Michael reaction has been developed. This strategy allows for the construction of isoindolines bearing several degrees of fluorination (mono-, di-, or trifluoromethyl as well as heavier fluorinated groups). In the majority of all cases, the products are formed as single isomers.
Chiral Brønsted Acid-Catalyzed Asymmetric Allyl(propargyl)boration Reaction of ortho-Alkynyl Benzaldehydes: Synthetic Applications and Factors Governing the Enantioselectivity
Chiral Bronsted acid-catalyzed allyl(propargyl)boration of ortho-alkynyl benzaldehydes gives rise to ω-alkynyl homoallylic(homopropargylic)alcohols that can be further transformed to complex molecular scaffolds via subsequent hydroalkoxylation, ring-closing enyne metathesis (RCEYM), or intramolecular Pauson–Khand reaction (PKR). Optimizations of each two-step transformation is reported. A strong dependence between enantioselectivities and the nature of the substitution at the alkynyl moiety is observed, showcasing that the triple bond is not merely a spectator in this transformation. Density functional theory (DFT) calculations (M06-2X/6-311+G(d,p)–IEFPCM//B3LYP/6-31G(d)) show that this dep…
Relay Catalysis: Enantioselective Synthesis of Cyclic Benzo-Fused Homoallylic Alcohols by Chiral BrOnsted Acid-Catalyzed Allylboration/Ring Closing Metathesis
Six- and seven-membered benzo-fused cyclic homoallylic alcohols can be readily synthesized by a tandem chiral BrOnsted acid-catalyzed allyl (crotyl)boration/ring closing metathesis sequence performed under orthogonal relay catalysis conditions. Excellent enantio- and diastereoselectivities are obtained in most of the cases. In addition, the parent crotylboration/RCM process is also described. The required substrates, ortho-vinylbenzaldehydes, are readily available in one step from commercially available starting materials. Both catalysts and reactants are also available from commercial suppliers. The reaction shows broad functional group compatibility and is also suitable for heteroaromatic…
Asymmetric Allylation/Ring Closing Metathesis: One-Pot Synthesis of Benzo-fused Cyclic Homoallylic Amines. Application to the Formal Synthesis of Sertraline Derivatives
A one-pot asymmetric allylation/ring closing metathesis (RCM) sequence for the synthesis of cyclic homoallylic amines has been developed. A library of six- and seven-membered benzo-fused products has been synthesized in good yields and complete diastereoselectivity. The new methodology has been applied to the formal syntheses of the antidepressant Sertraline and the epimeric Norsertraline. The methodology is amenable for the synthesis of analogs.
Intramolecular Michael reaction of tert-butylsulfinyl ketimines: asymmetric synthesis of 3-substituted indanones.
Aromatic tert-butylsulfinyl ketimines bearing a suitable Michael acceptor at the ortho position readily undergo an intramolecular conjugate addition achieving indanone derivatives in good yields and complete diastereoselectivity.
ChemInform Abstract: Base-Dependent Stereodivergent Intramolecular Aza-Michael Reaction: Asymmetric Synthesis of 1,3-Disubstituted Isoindolines.
For the reaction of the compounds (I) the careful choice of the base allows the exclusive formation of either cis or trans diastereoisomer with the exception of the trihalogenates (Ie) and (If), which afford the cis-products regardless of the base used.
CCDC 1031785: Experimental Crystal Structure Determination
Related Article: Pablo Barrio, Elsa Rodríguez, Kodai Saito, Santos Fustero, Takahiko Akiyama|2015|Chem.Commun.|51|5246|doi:10.1039/C4CC08598A
CCDC 935857: Experimental Crystal Structure Determination
Related Article: Santos Fustero, Lidia Herrera, Ruben Lázaro, Elsa Rodríguez, Miguel A. Maestro, Natalia Mateu, Pablo Barrio|2013|Chem.-Eur.J.|19|11776|doi:10.1002/chem.201301591
CCDC 1434367: Experimental Crystal Structure Determination
Related Article: Elsa Rodríguez, Matthew N. Grayson, Amparo Asensio, Pablo Barrio, K. N. Houk, and Santos Fustero|2016|ACS Catalysis|6|2506|doi:10.1021/acscatal.6b00209
CCDC 1434366: Experimental Crystal Structure Determination
Related Article: Elsa Rodríguez, Matthew N. Grayson, Amparo Asensio, Pablo Barrio, K. N. Houk, and Santos Fustero|2016|ACS Catalysis|6|2506|doi:10.1021/acscatal.6b00209