Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• product. Later, it was found that trifluoromethyl ketimines 26 also function as electrophiles under similar reaction conditions [28]. Although initial attempts of asymmetric transformations were not successful, enantioselective cross-benzoin reactions of heteroaromatic aldehydes (acyl donors) and aryl

• problem was successfully addressed by using a hindered base, pentamethyl piperidine, which was inert towards the products (Scheme 24) [40]. In 2013, Ye disclosed a remarkable NHC-catalysed enantioselective aza-benzoin reaction of enals and activated ketimines leading to the formation of functionalised α

• adduct. A variety of trifluoromethylated α-aminoketones could be synthesised in enantiomerically pure form using this method (Scheme 25). Isatin derived ketimines 41 were employed as electrophiles in the NHC-catalysed chemo- and stereoselective cross-aza-benzoin reaction with enals by Chi. The reaction

Cupreines and cupreidines: an established class of bifunctional cinchona organocatalysts

• Laura A. Bryant,
• Rossana Fanelli and
• Alexander J. A. Cobb

Beilstein J. Org. Chem. 2016, 12, 429–443, doi:10.3762/bjoc.12.46

• this work, Shi, Li and co-workers partnered the isatin derived N-Boc ketimines 8 with MVK (6, Scheme 3a) to obtain the corresponding adducts 9 with very good selectivity [22]. Interestingly, replacing the Boc group with an ethyl carbamate decreased the yield and enantioselectivity dramatically, as did

Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

• Qing He,
• Gu Zhan,
• Wei Du and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2016, 12, 309–313, doi:10.3762/bjoc.12.33

• stereocontrol [6][7][8][9][10][11][12]. Maleimides are also good nucleophilic precursors in the MBH reactions and in 2013, Chimni developed an asymmetric MBH reaction of isatins and maleimides with excellent enantioselectivity [13]. Later, the same group expanded this strategy to isatin-derived ketimines under

A convergent, umpoled synthesis of 2-(1-amidoalkyl)pyridines

• Tarn C. Johnson and
• Stephen P. Marsden

Beilstein J. Org. Chem. 2016, 12, 1–4, doi:10.3762/bjoc.12.1

• 4 [5] and the threonine tyrosine kinase inhibitor CFI-401870 (5) [6]. The 2-(1-amidoalkyl)pyridines are almost always synthesised by acylation of the related 2-(1-aminoalkyl)pyridines, which can be prepared by reduction of ketimines derived from 2-acylpyridines [5] or 2-cyanopyridines [6], addition

Copper-catalyzed aerobic radical C–C bond cleavage of N–H ketimines

• Ya Lin Tnay,
• Gim Yean Ang and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2015, 11, 1933–1943, doi:10.3762/bjoc.11.209

• cleavage of N–H ketimines. Treatment of N–H ketimines having an α-sp3 hybridized carbon under Cu-catalyzed aerobic reaction conditions resulted in a radical fragmentation with C–C bond cleavage to give the corresponding carbonitrile and carbon radical intermediate. This radical process has been applied for

• the construction of oxaspirocyclohexadienones as well as in the electrophilic cyanation of Grignard reagents with pivalonitrile as a CN source. Keywords: C–C bond cleavage; copper; ketimines; molecular oxygen; radical; Introduction Alkylideneaminyl radicals (iminyl radicals) have been utilized for

• precursors when we started our studies on the oxidative reactions of N–H ketimines [43][44][45][46][47][48][49] (Scheme 1d). The generation of iminyl radicals by single-electron oxidation of N–H ketimines appears to be the most atom economical method, since only protons (H+) are produced along with the

Multicomponent versus domino reactions: One-pot free-radical synthesis of β-amino-ethers and β-amino-alcohols

• Bianca Rossi,
• Nadia Pastori,
• Simona Prosperini and
• Carlo Punta

Beilstein J. Org. Chem. 2015, 11, 66–73, doi:10.3762/bjoc.11.10

• procedure, an aryl amine, a ketone, and a cyclic ether or an alcohol molecule are assembled in a one-pot synthesis by nucleophilic radical addition of ketyl radicals to ketimines generated in situ. The reaction occurs under mild conditions by mediation of the TiCl4/Zn/t-BuOOH system, leading to the

• TiCl3 proved particularly effective for promoting the formation and functionalization of aldimines (Scheme 1, entry a), but was necessarily replaced with the redox TiCl4 (CH2Cl2)/Zn system when operating in the presence of ketones (Scheme 1, entry b), as the corresponding ketimines were more sensitive

• the results of our in depth investigation to allow for the one-pot multicomponent addition of alcohols and ethers to ketimines generated in situ, by inhibition of the domino reaction. Results and Discussion The optimization of the multicomponent approach was conducted by the one-pot assembly of p

Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

• Radhey M. Singh,
• Kishor Chandra Bharadwaj and
• Dharmendra Kumar Tiwari

Beilstein J. Org. Chem. 2014, 10, 2975–2980, doi:10.3762/bjoc.10.315

• and in 91% yield in just 3 hours of reaction (Table 2, entry 1) was achieved. Encouraged by these results, the focus was shifted to the development of this aza-Morita–Baylis–Hillman reaction using isatin-derived ketimines [51][52][53]. This reaction could also lead to the construction of tertiary

A convenient enantioselective decarboxylative aldol reaction to access chiral α-hydroxy esters using β-keto acids

• Zhiqiang Duan,
• Jianlin Han,
• Ping Qian,
• Zirui Zhang,
• Yi Wang and
• Yi Pan

Beilstein J. Org. Chem. 2014, 10, 969–974, doi:10.3762/bjoc.10.95

• aldehydes and carboxylic acids. Other less reactive carbonyl derivatives such as isatins [11][12], ketimines [13] and sulfonylimines [14] have also been employed with β-keto acids in the decarboxylative addition processes. α-Keto esters as surrogates of aldehydes for the generation of chiral alcohols by

Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines

• Alexander Penger,
• Cortney N. von Hahmann,
• Alexander S. Filatov and
• John T. Welch

Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303

• availability of the α-pentafluorosulfanyl carbonyl compounds facilitated an effort to dramatically expand the utility of these intriguing materials by synthesis and characterization of the corresponding pentafluorosulfanylated β-lactams. α-SF5-Substituted aldimines and ketimines The aldehydes 1 were readily

• careful filtration of the desiccant, the dichloromethane solution of the imine was used in further reactions without purification or separation of unreacted amine or the enamine side product. Ketene imine cycloaddition reactions of α-SF5-substituted aldimines and ketimines Dropwise addition of the crude

An investigation of the observed, but counter-intuitive, stereoselectivity noted during chiral amine synthesis via N-chiral-ketimines

• Thomas C. Nugent,
• Richard Vaughan Williams,
• Andrei Dragan,
• Alejandro Alvarado Méndez and
• Andrei V. Iosub

Beilstein J. Org. Chem. 2013, 9, 2103–2112, doi:10.3762/bjoc.9.247

Copper-catalyzed aerobic aliphatic C–H oxygenation with hydroperoxides

• Pei Chui Too,
• Ya Lin Tnay and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2013, 9, 1217–1225, doi:10.3762/bjoc.9.138

• tertiary C–H bonds, respectively (Scheme 1b) [8][9]. Stimulated by these remote sp3 C–H oxidation reactions using the nitrogen-centered radicals derived from amidines and ketimines, we became interested to utilize oxygen-centered radicals (O-radicals) for the sp3 C–H functionalization. In this context, we

• direct 1,4-dioxygenation of alkane 10 was demonstrated by using the present method. Further studies will be carried out to develop more robust and efficient catalytic aerobic radical transformations for polyol synthesis from rather simple alkanes. Aliphatic C–H oxidation with amidines and ketimines by

Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives

• Martina Bonsignore,
• Maurizio Benaglia,
• Laura Raimondi,
• Manuel Orlandi and
• Giuseppe Celentano

Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71

• testing the commercially available N-Boc-L-proline (1) as catalyst in the reduction of ketimines with trichlorosilane. The imines were typically prepared with a microwave-promoted reaction between acetophenone and the aromatic amine in toluene in the presence of K10 clay as activator. The first screening

The use of chiral lithium amides in the desymmetrisation of N-trialkylsilyl dimethyl sulfoximines

• Matthew J. McGrath and
• Carsten Bolm

Beilstein J. Org. Chem. 2007, 3, No. 33, doi:10.1186/1860-5397-3-33

• potential for use in asymmetric catalysis. Results Asymmetric deprotonation of N-trialkylsilyl dimethyl sulfoximines with either enantiomer of lithium N,N-bis(1-phenylethyl)amide in the presence of lithium chloride affords enantioenriched sulfoximines on electrophilic trapping. Ketones, ketimines