Conjugate addition–enantioselective protonation reactions

• James P. Phelan and
• Jonathan A. Ellman

Beilstein J. Org. Chem. 2016, 12, 1203–1228, doi:10.3762/bjoc.12.116

• James P. Phelan Jonathan A. Ellman Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT 06520, USA 10.3762/bjoc.12.116 Abstract The addition of nucleophiles to electron-deficient alkenes represents one of the more general and commonly used strategies for the convergent

• assembly of more complex structures from simple precursors. In this review the addition of diverse protic and organometallic nucleophiles to electron-deficient alkenes followed by enantioselective protonation is summarized. Reactions are first categorized by the type of electron-deficient alkene and then

Copper-catalyzed asymmetric conjugate addition of organometallic reagents to extended Michael acceptors

• Thibault E. Schmid,
• Sammy Drissi-Amraoui,
• Christophe Crévisy,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 2418–2434, doi:10.3762/bjoc.11.263

• control of the regio- and enantioselectivity of the addition. The aim of this review is to report recent breakthroughs achieved in this challenging field. Keywords: conjugate additions; electron-deficient alkenes; enantioselective catalysis; extended Michael acceptors; organometallic nucleophiles

• ; sequential addition; Introduction Amongst the variety of synthetic methods available for the formation of C–C or C–heteroatom bonds, the asymmetric conjugate addition (ACA) of nucleophiles to electron-deficient alkenes is one of the most relevant and versatile for the synthesis of complex chiral molecules

• electron-deficient alkenes are Michael acceptors of high synthetic interest. Indeed, they can undergo successive nucleophilic additions and therefore enable the generation of several new chiral centers [3]. On the other hand, the main challenge associated with polyenic Michael acceptors lies within the

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines

• included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas. Keywords: carboxylic acids; free radicals

• radicals (RCH2)2NC•HR that added to electron deficient alkenes so facilitating several C–C bond forming and ring closing reactions [43][44]. N-Methyl- and N-tert-butylpyrrolidine (5a and 5b) both added to the α,β-unsaturated menthyloxyfuranone 6 producing of pyrrolidinyldihydrofuranones 7 in good yields

One-pot odourless synthesis of thioesters via in situ generation of thiobenzoic acids using benzoic anhydrides and thiourea

• Mohammad Abbasi and
• Reza Khalifeh

Beilstein J. Org. Chem. 2015, 11, 1265–1273, doi:10.3762/bjoc.11.141

• the reaction of benzoic anhydrides, thiourea and various organic halides (primary, allylic, and benzylic) or structurally diverse, electron-deficient alkenes (ketones, esters, and nitriles) in the presence of Et3N has been developed. In this method, thiobenzoic acids were in situ generated from the

• reaction of thiourea with benzoic anhydrides, which were subjected to conjugate addition with electron-deficient alkenes or a nucleophilic displacement reaction with alkyl halides. Keywords: benzoic anhydride; Michael addition; nucleophilic displacement; thioester; thiourea; Introduction Thioesters have

• anhydride) after extractive work-up with EtOAc followed by silica gel column chromatography. The optimized reaction conditions were then applied to further reactions using structurally diverse benzoic anhydrides and different electron-deficient alkenes. The results are summarized in Table 1. It can be seen

Matsuda–Heck reaction with arenediazonium tosylates in water

• Ksenia V. Kutonova,
• Marina E. Trusova,
• Andrey V. Stankevich,
• Pavel S. Postnikov and
• Victor D. Filimonov

Beilstein J. Org. Chem. 2015, 11, 358–362, doi:10.3762/bjoc.11.41

• . High yields for electron-deficient alkenes and moderate yields for electron-rich alkenes were obtained. The reaction has a broad range and gives the desired products with a high purity. Experimental All starting materials were ACS grade and were employed without further purification. Arenediazonium

Chiral phosphines in nucleophilic organocatalysis

• Yumei Xiao,
• Zhanhu Sun,
• Hongchao Guo and
• Ohyun Kwon

Beilstein J. Org. Chem. 2014, 10, 2089–2121, doi:10.3762/bjoc.10.218

• ] annulation by combining MBH carbonates and electron-deficient alkenes into a single molecule (Scheme 37) [73]. In the presence of 10 mol % of D3, a variety of α,β-unsaturated carbonyl compounds were transformed efficiently in toluene at −5 °C to give optically active benzobicyclo[4.3.0] compounds 5 in

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• considerable number of pacidamycin analogues. 4. The multicomponent domino reactions initiated by the Knoevenagel condensation The Knoevenagel condensation can be considered as one of the most useful tools for the formation of C=C double bonds. The condensation products, i.e., electron-deficient alkenes

The chemistry of amine radical cations produced by visible light photoredox catalysis

• Jie Hu,
• Jiang Wang,
• Theresa H. Nguyen and
• Nan Zheng

Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234

• interception by a variety of nucleophiles to directly install a new bond at the position α to the nitrogen atom. In contrast, α-amino radical 3 is nucleophilic. It tends to add to electron-deficient alkenes to form a C–C bond, also at the position α to the nitrogen atom. This review will summarize the work to

[3 + 2]-Cycloadditions of nitrile ylides after photoactivation of vinyl azides under flow conditions

• Stephan Cludius-Brandt,
• Lukas Kupracz and
• Andreas Kirschning

Beilstein J. Org. Chem. 2013, 9, 1745–1750, doi:10.3762/bjoc.9.201

• likely proceeds via the respective 2H-azirines by photoinduced in-situ formation and subsequent heterolytic ring opening. The resulting 1,3-dipole is trapped directly with electron-deficient alkenes to form the [2 + 3] cycloaddition products. With this method, we were able to prepare a variety of

• azides 1 from alkenes 6 under flow conditions [9]. Schematic presentation of the flow set-up for the synthesis of 2H-azirines 2 under inductive heating (IH, left) and photochemical (hν, right) conditions. Photoinduced cycloadditions of vinyl azides 1a–f and electron-deficient alkenes 4a–d. All

Diastereoselective synthesis of nitroso acetals from (S,E)-γ-aminated nitroalkenes via multicomponent [4 + 2]/[3 + 2] cycloadditions promoted by LiCl or LiClO₄

• Leandro Lara de Carvalho,
• Robert Alan Burrow and
• Vera Lúcia Patrocinio Pereira

Beilstein J. Org. Chem. 2013, 9, 838–845, doi:10.3762/bjoc.9.96

• nitroalkenes 5a–c as heterodienes, ethyl vinyl ether (EVE) as a dienophile, and selected electron-deficient alkenes as 1,3-dipolarophiles. The employment of different organic solutions of LiClO4 or LiCl as promoter systems provided the respective nitroso acetals with yields from 34–72% and good levels of

• as 3 (R2 = alkyl) were employed in various synthetic transformations [6][7] (Scheme 1). In addition, Denmark’s group and others investigated the tandem [4 + 2]/[3 + 2] nitroalkene cycloaddition employing unactivated olefins or enol ethers as dienophiles and electron-deficient alkenes as 1,3

• -diamines [19]. Herein, we report the reactivity and diastereoselectivity of 5a–c as heterodienes in a multicomponent [4 + 2]/[3 + 2] cycloaddition with ethyl vinyl ether (EVE) and selected electron-deficient alkenes in the presence of LiCl or LiClO4 as promoters. A study on the solvent effect was also

Chiral multifunctional thiourea-phosphine catalyzed asymmetric [3 + 2] annulation of Morita–Baylis–Hillman carbonates with maleimides

• Hong-Ping Deng,
• De Wang,
• Yin Wei and
• Min Shi

Beilstein J. Org. Chem. 2012, 8, 1098–1104, doi:10.3762/bjoc.8.121

• ] have also developed asymmetric [3 + 2] annulations of allenoates to give the corresponding cyclopentene derivatives in good yields with excellent enantioselectivities [37]. On the other hand, some examples of phosphine-catalyzed [3 + 2] annulation of MBH carbonates with electron-deficient alkenes have

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• favored [71][72]. Substituted olefins may add in an exo or endo fashion. While electron-deficient alkenes give mixtures of both possible products, electron-rich compounds show stereoselectivity towards the exo products (Scheme 22) [73]. Ortho photocycloaddition can, however, also take place from the