Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines

• Marco Manenti,
• Leonardo Lo Presti,
• Giorgio Molteni and
• Alessandra Silvani

Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34

• oxindoles [7][8][9][10][11] and also of aminoboronic acids [12], we recently exploited a molecular hybridization strategy to synthesize chiral oxindole-based β-aminoboronic acids and spiro derivatives [13]. Apart from our work and a quite recent report describing a useful Cu-catalyzed enantioselective

Iridium-catalyzed hydroacylation reactions of C1-substituted oxabenzonorbornadienes with salicylaldehyde: an experimental and computational study

• Angel Ho,
• Austin Pounder,
• Krish Valluru,
• Leanne D. Chen and
• William Tam

Beilstein J. Org. Chem. 2022, 18, 251–261, doi:10.3762/bjoc.18.30

• intermediates have found use in the total synthesis of (+)-norchelidonine (an isoquinoline alkaloid) [55], sertraline (an antidepressant) [56], and arnottin I (an anti-inflammatory) [57]. Although OBD 1 has been shown to undergo many different modes of reactivity in both a stereo- and enantioselective manner

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• undoubtedly the most efficient way to prepare chiral compounds that our society requires as medicines, materials, or crop protecting agents. Traditionally, enzymes and metal complexes with chiral ligands served as the main type of enantioselective catalysts. Even though small chiral organic compounds have

• early to stimulate greater developments. Things started to change in the late 1990s when short-chain peptides [3], carbohydrate-based ketones [4][5], and thioureas [6] were shown to catalyze enantioselective transformations. The real breakthrough came in the year 2000 when two teams independently

• cyclopropenimines exemplify Brønsted base organocatalysts that are useful for diverse reactions not easily accessible by other means. Here, Lambert and co-workers employed this type of catalyst in the formation of pyroglutamates via enantioselective Michael addition of amino ester imines [22]. Phase-transfer

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• 226031, India Academy of Scientific and Innovative Research, Ghaziabad, 201002, India 10.3762/bjoc.18.25 Abstract A practical enantioselective N-selective nitroso aldol reaction of α-methylmalonamates with a nitrosoarene is reported. The reaction employs the Takemoto thiourea catalyst for the induction

• of enantioselectivity, and the corresponding optically active oxyaminated malonamates were obtained in reasonably good yields. Keywords: enantioselective; malonamate; nitroso aldol reaction; N-selectivity; Takemoto catalyst; Introduction Nitrosoarenes are versatile building blocks frequently

• achieve optically active α-aminoxy and α-hydroxyamino carbonyl compounds has received considerable attention in the past decades [24]. In 2003, the Yamamoto group demonstrated for the first time that nitrosobenzene could be used as a practical reagent for the catalytic enantioselective α-aminoxylation

Asymmetric organocatalytic Michael addition of cyclopentane-1,2-dione to alkylidene oxindole

• Estelle Silm,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2022, 18, 167–173, doi:10.3762/bjoc.18.18

• presence of a multifunctional squaramide catalyst. Michael adducts were obtained in high enantioselectivities and in moderate diastereoselectivities. Keywords: cyclopentane-1,2-dione; enantioselective catalysis; Michael addition; organocatalysis; squaramide; Introduction Diketones are generally very

Bifunctional thiourea-catalyzed asymmetric [3 + 2] annulation reactions of 2-isothiocyanato-1-indanones with barbiturate-based olefins

• Jiang-Song Zhai and
• Da-Ming Du

Beilstein J. Org. Chem. 2022, 18, 25–36, doi:10.3762/bjoc.18.3

• or new methodologies to construct the spirobarbiturates with diverse structures. In recent years, good progress has been achieved in the construction of racemates of spirobarbiturates and the enantioselective synthesis [24][25][26][27][28][29], but only limited progress has been made in the

• % ee) could still be maintained (Scheme 6b). This one-pot three-component reaction would be more convenient for potential industrial applications. Finally, in order to understand the enantioselective formation process of product 3, we proposed the possible mechanisms for the [3 + 2] cyclization

• to form intermediate B. Finally, the catalyst C4 is removed in intermediate C and the product 3aa is obtained. Conclusion In summary, we have successfully developed an exceptionally efficient strategy for the enantioselective construction of indanone-derived spirobarbiturates through a simple

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• . Alemán and co-workers also published the use of a photogenerated DABCO radical cation in a distal β-carbonyl enantioselective C–H functionalization for the synthesis of pyrroline derivatives [26] (Figure 2d). The latter is, to the best of our knowledge, the only work reporting a direct substrate C–H bond

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• active compounds in medicinal chemistry and as chiral ligands in asymmetric catalysis. Chiral phosphoric acids are recognized as efficient organocatalysts for a variety of enantioselective transformations. In this review, we summarize the recent development of chiral phosphoric acid-catalyzed synthesis

• -catalyzed enantioselective transformations [9][14][22][23]. Axial chirality is also found in chiral stationary phases for enantioselective separation, dopants in liquid-crystalline materials, chiroptical molecular switches, microporous soluble polymers, and interlocked nanotubes (Figure 3) [24]. In addition

• catalysts for a variety of enantioselective transformations, especially for carbon–carbon and carbon–heteroatom bond-forming reactions [15][28]. They are important for the development of axially chiral compounds, which are involved in the design of chiral catalysts and ligands. Currently, chiral phosphoric

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• arylacetaldimines of phenylethylamines [2] (Figure 1). Especially the Pictet–Spengler reaction has attracted considerable interest in chemistry and drug development in recent years, and modern methods like enantioselective approaches, organocatalysis, and enzymatic methods have been introduced by numerous groups [3

• enantioselective organocatalysis based on Jacobsen’s pioneering work [56]. Since we had recently identified substituted 1-benzyltetrahydroisoquinolines as truncated analogues of bioactive bisbenzylisoquinoline alkaloids (SG-005 and SG-094) as TPC2 blockers with antiproliferative activity, we tested our alkaloids

Synthetic strategies toward 1,3-oxathiolane nucleoside analogues

• Umesh P. Aher,
• Dhananjai Srivastava,
• Girij P. Singh and
• Jayashree B. S

Beilstein J. Org. Chem. 2021, 17, 2680–2715, doi:10.3762/bjoc.17.182

• surfactant. Exceptionally, the end product was obtained in 99.9% ee by using whole-cell Klebsiella oxytoca catalysis and enantioselective resolution of the racemic mixture at 30 °C, pH 7.0, a substrate concentration of 1.5 g/L, and no additives. As compared to nearly all of the lipase-catalyzed methods to

• process that reached 96.5% ee through the combination of the reversible hemithioacetal transformation and the enantioselective lactonization catalyzed by the immobilized lipase from Trichosporon laibachii (Scheme 24). As a result, the desired stereochemistry of 1,3-oxathiolane precursors 71 and 72 was

• -189 (1c) showed potent anti-HIV-1 activity. The EC50 value of (±)-BCH-189 (1c) was reported to be in the range of 0.37–1.31 µM (mean 0.73 µM), and the compound was effective against HIV-1 in MT-4 cells [13]. Enantioselective enzymatic synthesis of 3TC (1) was also reported by Milton et al. [47], who

Solvent-free synthesis of enantioenriched β-silyl nitroalkanes under organocatalytic conditions

• Akhil K. Dubey and
• Raghunath Chowdhury

Beilstein J. Org. Chem. 2021, 17, 2642–2649, doi:10.3762/bjoc.17.177

• Akhil K. Dubey Raghunath Chowdhury Bio-Organic Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India Homi Bhabha National Institute, Anushaktinagar, Mumbai-400094, India 10.3762/bjoc.17.177 Abstract An enantioselective 1,4-conjugate addition of nitromethane to β-silyl α,β

• organosilanes [2][7][8][9][10][11][12][13][14]. A number of efficient catalytic enantioselective methods has been developed for the synthesis of chiral organosilanes [15][16][17][18][19][20][21][22][23][24]. Out of the chiral organosilanes, nitrosilanes are important synthetic targets as they are precursors of

• -nitrosilanes through a Cu(II)–chiral bipyridine complex catalyzed enantioselective silyl transfer reaction to nitroalkenes using Suginome’s silylboron reagent (Scheme 1a) [28]. Recently, we have reported the synthesis of chiral β-nitrosilanes via an organocatalytic conjugate addition of nitromethane to β

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• , including enantioselective H-bonding-catalyzed additions to aliphatic N-Boc-imines with high stereoselectivity [22]. A broad range of β-aminonitroolefins were reduced to chiral β-aminonitroalkanes in high yields and excellent enantioselectivities using trichlorosilane as a reducing agent and an N

• Michael addition of thioacetic acid to aromatic and aliphatic nitroalkenes to produce chiral β-aminothiols, compounds of pharmaceutical interest [26]. Similarly, the enantioselective addition of thioacids to trisubstituted nitroalkenes was catalyzed by several N-sulfinylureas providing the 1,2

• ): [M − CF3COOH + H]+ calcd for C12H22F3N3O4S, 248.1427; found, 248.1424. Representative procedure for enantioselective Michael additions under solution conditions The catalyst (0.015 mmol) and base (NMM, 2 mg, 0.015 mmol) were dissolved in the solvent (0.7 mL) and, after 10 min, the nitroalkene (0.5

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• appears that in this case, both activation mechanisms, namely through hydrogen bonding and iminium ion formation are operating. Using the same chiral cinchona-based primary-tertiary diamine as catalyst (cat. 11), Zhai et al. developed a highly efficient intramolecular enantioselective aza-Michael addition

• also and pentafluoropropionic acid (PFP) was used as a co-catalyst. In the presence of 1,4-dioxane solvent, products chiral 3-substituted 1,2-oxazinanes (16) were obtained in 99% yield with good ee of 96% (Scheme 2) [31]. Following a similar strategy, Ma et al. accomplished a highly enantioselective

• active tetrahydrobenzofuro[3,2-b]quinolines and tetrahydrobenzo[4,5]thieno[3,2-b]quinolines 33 in high yields ranging from 35–99% and excellent diastereo- (>20:1 dr), and enantioselectivities (up to ≈99% ee) (Scheme 3) [38]. Roy et al. accomplished an enantioselective intramolecular aza-Michael addition

α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions

• Scott Benz and
• Andrew S. Murkin

Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172

• catalyst in the presence of a substrate possessing a prochiral migrating group or (2) stereospecifically by means of a chiral α-ketol. As an example of an enantioselective rearrangement, complexes of nickel(II) with a series of chiral 1,2-diaminopropane or pyridineoxazoline ligands were evaluated for their

• with greater than 80% ee. As a third example of an enantioselective α-ketol rearrangement, Dai et al. used a chiral Al(III) catalyst to induce the rearrangement of 3 (Ar = Ph) and several aryl derivatives 9 (Figure 4) [6]. Among the N,N′-dioxide ligands explored, 11, which was derived from ʟ

• -moderate yields but with ≥74% ee, while the α-amino ketone products 15 could be obtained in nearly quantitative yields and variable ee, from 53% to 98% [6]. A fifth example of an enantioselective α-ketol rearrangement provides a twist by demonstrating the ability to function on substrates protected as

Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines

• Zhen-Sheng Jia,
• Qiang Yue,
• Ya Li,
• Xue-Tao Xu,
• Kun Zhang and
• Bing-Feng Shi

Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165

• in 2020, an enantioselective C–H annulation of ferrocenylformamides with alkynes was achieved by the Ye group enabled by Ni-Al bimetallic catalysis and a chiral secondary phosphine oxide (SPO) ligand [35]. Hou et al. also reported the asymmetric C−H alkenylation of quinoline- and pyridine-substituted

Recent advances in the tandem annulation of 1,3-enynes to functionalized pyridine and pyrrole derivatives

• Yi Liu,
• Puying Luo,
• Yang Fu,
• Tianxin Hao,
• Xuan Liu,
• Qiuping Ding and
• Yiyuan Peng

Beilstein J. Org. Chem. 2021, 17, 2462–2476, doi:10.3762/bjoc.17.163

• annulation. Recently, there have been several elegant reviews covering the 1,3-enynes chemistry [46][47][48]. For instance, Procter and co-workers reviewed the copper-catalyzed functionalization of enynes [46]. In 2020, the Wang group reviewed the development of 2-activated 1,3-enyne in enantioselective

Targeting active site residues and structural anchoring positions in terpene synthases

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

• of cross peaks in blue and in red refers to the hydrogens in Scheme 1 of same colour. Determination of the enantiomeric composition of 8 and 9 obtained from GGPP with SmTS1 enzyme variants through enantioselective labelling with (R)- and (S)-(1-13C,1-2H)GGPP. Compound 8 is obtained with different

Enantioselective PCCP Brønsted acid-catalyzed aminalization of aldehydes

• Martin Kamlar,
• Robert Reiberger,
• Martin Nigríni,
• Ivana Císařová and
• Jan Veselý

Beilstein J. Org. Chem. 2021, 17, 2433–2440, doi:10.3762/bjoc.17.160

• Abstract Here we present an enantioselective aminalization of aldehydes catalyzed by Brønsted acids based on pentacarboxycyclopentadienes (PCCPs). The cyclization reaction using readily available anthranilamides as building blocks provides access to valuable 2,3-dihydroquinazolinones containing one

• enantioselective synthetic strategies towards 2,3-dihydroquinazolinone derivatives has drawn the attention of organic chemists for a long time [14][15][16][17][18], even though the aminal stereocenter is sensitive to racemization [12]. The well-established and straightforward approach in the asymmetric

• is the binaphthol (BINOL)-derived phosphoric acid class of catalysts, firstly reported by Akiyama [25] and Terada [26]. Soon after, BINOL-derived phosphoric acids were employed in the enantioselective synthesis of 2,3-dihydroquinazolinones. The initial report in this area was made by List and co

Strategies for the synthesis of brevipolides

• Yudhi D. Kurniawan and
• A'liyatur Rosyidah

Beilstein J. Org. Chem. 2021, 17, 2399–2416, doi:10.3762/bjoc.17.157

• . Eventually, trans-crotonaldehyde (62) is selected as the precursor for this study. The study began with the enantioselective epoxidation of trans-crotonaldehyde (62) under Jørgensen conditions using organocatalyst 63, followed by a two-carbon homologation to obtain α,β-unsaturated epoxy ester 64 in 78% yield

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• cyclization reactions, there were examples where a Hg(II)-salt-mediated cyclization had been successfully employed as one of the important steps during the total synthesis of natural products. In 1998, a highly enantioselective total synthesis of (+)-furanomycin (190) was achieved through Hg(TFA)2-promoted

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

• ester moieties at C-3 have been shown to participate in enantioselective phase-transfer-catalysed alkylations promoted by ad-hoc designed quaternary ammonium salts derived from quinine bearing hydrogen-bond donating substituents. For the first time in such phase-transfer-catalysed enolate alkylations

• of HBr in these processes. The influence of steric and electronic factors from both the perspective of the nucleophile and electrophile were investigated and levels of enantiocontrol up to 90% ee obtained. The synthetic utility of the methodology was demonstrated via the concise enantioselective

• highly valuable synthetic building blocks [5][6][7][8][9][10][11][12]. Both pyrroloindolines 1 and spirooxindoles 2 are conceivably available from key 3,3-disubstituted intermediates 3, which could be prepared via an enantioselective SN2 alkylation involving enolate 3a (Figure 1B). The versatility of

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• participates in the ionization step by an anion abstraction-type process (Figure 2b). In the latter approach, the C–X bond cleavage can then either follow a SN1 or SN2 pathway. For enantioselective purposes, solvation of the ion pair is crucial for obtaining high stereoinduction. While more polar solvents give

• chiral contact-ion pair can be formed, which is necessary for the transfer of the chiral information to the product. As a consequence, most of the reported methods embracing enantioselective anion-binding catalysis rely on the use of nonpolar solvents such as ethers or aromatic compounds. Pioneering work

• halide anions can also engage as the nucleophile, which has been exploited in ring opening and related reactions (Figure 3b). In general, the idea of enantioselective ring opening produces two fixed stereocenters during one synthetic operation, increasing the complexity of the product significantly. This

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• arylated with moderate to good yields. When both primary and secondary C(sp3)‒H bonds are present in the substrate, regioselectivity favors the secondary position. The catalytic reaction conditions were compatible with the C(sp3)‒H arylation of tetrahydrothiophene (28a) as well [68]. The enantioselective C

• –H functionalization is a valuable method for synthesizing useful organic compounds from simple alkane starting materials [51][69][70]. Recently, Lu and co-workers reported an enantioselective benzylic C–H arylation method for synthesizing 1,1-diarylalkanes 26 via a photoredox and nickel dual

• under irradiation of blue LEDs at ambient temperature afforded the desired α-arylation products 32 from secondary amides 31 and (hetero)aryl bromides 3 (Scheme 18) [72]. The method showed a broad substrate scope for both amides and aryl bromides. The authors also realized the enantioselective variant of

Enantioenriched α-substituted glutamates/pyroglutamates via enantioselective cyclopropenimine-catalyzed Michael addition of amino ester imines

• Zara M. Seibel,
• Jeffrey S. Bandar and
• Tristan H. Lambert

Beilstein J. Org. Chem. 2021, 17, 2077–2084, doi:10.3762/bjoc.17.134

• Zara M. Seibel Jeffrey S. Bandar Tristan H. Lambert Department of Chemistry, Columbia University, New York, New York 10027, USA Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA 10.3762/bjoc.17.134 Abstract A procedure for the enantioselective synthesis

• substitution is discussed. Compared to other methods, this protocol allows for a broader and more enantioselective access to pyroglutamate derivatives. Keywords: Brønsted base; cyclopropenimine; enantioselective catalysis; Michael addition; pyroglutamate; Introduction α-Substituted glutamates have value as

• -substituted glutamate derivatives is via the Michael addition of α-amino ester enolates to acrylate acceptors. These products can also be easily converted to pyroglutamates by lactamization [28][29][30]. Although the use of substituted amino ester derivatives for the enantioselective α-alkylation has been