Base-free enantioselective S_N2 alkylation of 2-oxindoles via bifunctional phase-transfer catalysis

• Mili Litvajova,
• Emiliano Sorrentino,
• Brendan Twamley and
• Stephen J. Connon

Beilstein J. Org. Chem. 2021, 17, 2287–2294, doi:10.3762/bjoc.17.146

• catalysis, have been reported [24][25][26][27][28][29][30]. However, despite the excellent levels of enantiocontrol often achieved, in the majority of these studies the 2-oxindole subjected to enantioselective alkylation lacks the structural architecture necessary for further modifications (Scheme 1A

• investigating the effects of different solvents, bases and buffer systems, in preliminary experiments we were not able to prevent the non-catalysed benzylation of substrate 5; nevertheless, the enantioselective alkylation of 5 with benzyl bromide in the presence of a phase-transfer catalyst was attempted. This

• manipulations; C) This work: base-free enantioselective alkylation of 2-oxindoles 5. Enantioselective synthesis of a CRTH2 receptor antagonist. Catalyst evaluation. Electrophile scope. Supporting Information Supporting Information File 320: Experimental part. Funding This research emanated from investigations

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

Copper-catalyzed enantioselective conjugate addition of organometallic reagents to challenging Michael acceptors

• Delphine Pichon,
• Jennifer Morvan,
• Christophe Crévisy and
• Marc Mauduit

Beilstein J. Org. Chem. 2020, 16, 212–232, doi:10.3762/bjoc.16.24

• values were observed (20–36% ee), whereas no reactivity was observed with α,β-unsaturated amides. Although Pineschi’s conditions were ineffective for amides [49], Harutyunyan and co-workers achieved an important breakthrough by reporting the first enantioselective alkylation of α,β-unsaturated amides [50

A novel and practical asymmetric synthesis of eptazocine hydrobromide

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan,
• Kuaile Lin and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 2340–2347, doi:10.3762/bjoc.14.209

• in the presence of catalyst PTC (3). The designed synthesis is shown in Scheme 3. Two key reactions are included in this novel strategy: 1. the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone (2) with chloroacetonitrile generate 4 through the use of a phase-transfer catalyst; and 2. the

Enantioselective phase-transfer catalyzed alkylation of 1-methyl-7-methoxy-2-tetralone: an effective route to dezocine

• Ruipeng Li,
• Zhenren Liu,
• Liang Chen,
• Jing Pan and
• Weicheng Zhou

Beilstein J. Org. Chem. 2018, 14, 1421–1427, doi:10.3762/bjoc.14.119

• 10.3762/bjoc.14.119 Abstract In order to prepare asymmetrically (R)-(+)-1-(5-bromopentyl)-1-methyl-7-methoxy-2-tetralone (3a), a key intermediate of dezocine, 17 cinchona alkaloid-derived catalysts were prepared and screened for the enantioselective alkylation of 1-methyl-7-methoxy-2-tetralone with 1,5

One-pot functionalisation of N-substituted tetrahydroisoquinolines by photooxidation and tunable organometallic trapping of iminium intermediates

• Joshua P. Barham,
• Matthew P. John and
• John A. Murphy

Beilstein J. Org. Chem. 2014, 10, 2981–2988, doi:10.3762/bjoc.10.316

• volatilities of BrCCl3 and CHCl3 by removing them under vacuum and replacing the solvent. A solvent switch was also reported when photoredox activation of 4a was combined with thiourea-catalysed enantioselective alkylation [37]. The enantioselectivity of the thiourea-catalysed alkylation was optimal in non

Formal total syntheses of classic natural product target molecules via palladium-catalyzed enantioselective alkylation

• Yiyang Liu,
• Marc Liniger,
• Ryan M. McFadden,
• Jenny L. Roizen,
• Jacquie Malette,
• Corey M. Reeves,
• Douglas C. Behenna,
• Masaki Seto,
• Jimin Kim,
• Justin T. Mohr,
• Scott C. Virgil and
• Brian M. Stoltz

Beilstein J. Org. Chem. 2014, 10, 2501–2512, doi:10.3762/bjoc.10.261

• Engineering, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA, USA 10.3762/bjoc.10.261 Abstract Pd-catalyzed enantioselective alkylation in conjunction with further synthetic elaboration enables the formal total syntheses of a number of “classic” natural product target molecules

• will impact both academic and industrial settings, where the synthesis of stereogenic quaternary carbons is a continuing challenge. Keywords: enantioselective alkylation; natural products; palladium; Introduction Catalytic enantioselective allylic alkylation has emerged as a powerful method for the

• the antipode of (+)-12 using the palladium-catalyzed enantioselective alkylation chemistry described above. We commenced a formal total synthesis of (−)-thujopsene (10) with the goal of improved efficiency compared to the Srikrishna/Anebouselvy route and to use enantioselective palladium catalysis to

Preparation of phosphines through C–P bond formation

• Iris Wauters,
• Wouter Debrouwer and
• Christian V. Stevens

Beilstein J. Org. Chem. 2014, 10, 1064–1096, doi:10.3762/bjoc.10.106

• reactions of secondary phosphines with several electrophiles, including alkyl halides (alkylation), alkenes (hydrophosphination) and aryl iodides (arylation). Chan et al. synthesized P-stereogenic phosphine boranes using a ruthenium catalyst. The secondary phosphine 36a underwent an enantioselective

• alkylation to 12c (Scheme 11). The mechanism of the reaction is based on the formation of an electron-rich ruthenium–phosphido complex that enhances the nucleophilicity at the phosphorus atom. This permitted the reaction to proceed with the less electrophilic benzylic chlorides 35 instead of bromides. The

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• of sustainable radical-mediated chemical processes under very soft irradiation conditions (e.g., household fluorescence or LED bulbs, halogen lamps, sunlight, Xe lamp), e.g., enantioselective alkylation, cycloaddition, etc. [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Ruthenium- and iridium-based

Synthesis of enantiomerically enriched (R)-¹³C-labelled 2-aminoisobutyric acid (Aib) by conformational memory in the alkylation of a derivative of L-alanine

• Stephen P. Fletcher,
• Jordi Solà,
• Dean Holt,
• Robert A. Brown and
• Jonathan Clayden

Beilstein J. Org. Chem. 2011, 7, 1304–1309, doi:10.3762/bjoc.7.152

• Stephen P. Fletcher Jordi Sola Dean Holt Robert A. Brown Jonathan Clayden School of Chemistry, University of Manchester, Oxford Rd., Manchester M13 9PL, UK 10.3762/bjoc.7.152 Abstract The method of Kouklovsky and coworkers for the enantioselective alkylation of cyclic N-naphthoyl derivatives of

• Ar–CO axis as a chiral “aide-mémoire” for translating the configuration of the starting amino acid into the configuration of the product. We have previously employed benzamide and naphthamide Ar–CO axes in “chiral memory” processes [52][53]. Kouklovsky reported the enantioselective alkylation of

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• imine 7 in 67% yield. Under the aprotic conditions of the alkylation protocol, the silyl protecting group turned out to be stable, a fact which facilitated the purification of the imine 7. It is an obvious idea to apply the established protocols for the enantioselective alkylation of ester 6 under phase