Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

• Marco Mottinelli,
• Mathew P. Leese and
• Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

• of a reducing agent (NaBH(OAc)3). The preferential formation of 11 relative to imine reduction, even in the presence of an excess of reducing agent, suggests a rapid intramolecular rearrangement of an iminium derivative 12 to the highly activated ortho-position of the aromatic ring. The possible

Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

• Hanmo Zhang,
• E. Ben Hay,
• Stephen J. Geib and
• Dennis P. Curran

Beilstein J. Org. Chem. 2015, 11, 1649–1655, doi:10.3762/bjoc.11.181

• /fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3

• reactive imines like 14 in Figure 3 and stable imines like 2 (Figure 2) in the prior work is that the former imines have N-aryl groups while the latter have N-alkyl groups. This suggests that the N-aryl groups promote imine reduction. We speculate based on the two different types of products isolated from

• be effected by adding Lewis bases (such as HMPA) or by using Lewis acidic tin hydrides (such as Bu2SnClH) [16][17]. Potential catalysts of hydride reduction such as benzenesulfinic acid (PhSO2H) and tributyltin benzenesulfinate (PhSO2SnBu3) could form under these conditions [11]. The imine reduction

Streptopyridines, volatile pyridine alkaloids produced by Streptomyces sp. FORM5

• Ulrike Groenhagen,
• Michael Maczka,
• Jeroen S. Dickschat and
• Stefan Schulz

Beilstein J. Org. Chem. 2014, 10, 1421–1432, doi:10.3762/bjoc.10.146

• , e.g., via 31 followed by double bond reduction may lead to piperideine 24, a precursor of the major liquid phase component 22. Alternatively, this compound might originate from the reduced PKS precursor 32 that is transformed via 33 into 24. Piperidine 22 is then obtained via imine reduction as

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

• unequivocally supported this conclusion. The present study co-examines an alternative hypothesis, namely that some classes of cis-imines may hold conformations that erode the inherent facial bias of the chiral auxiliary, providing more of the trans-imine reduction product than would otherwise be expected. The

• ensuing experimental and computational (DFT) results favor the former, pre-existing, explanation. Keywords: chiral amines; cis/trans isomerization; imine isomerization; imine reduction; reductive amination; Introduction A class of chiral compounds drawing ever more attention is α-chiral amines (chiral

• , nitrogen C–H insertion [10][11][12], hydroamination [13][14][15][16], hydroaminoalkylation [17][18], reductive amination [19][20][21][22][23], and enamine reduction [23][24][25][26][27] are experiencing a renaissance; while imine reduction [23][28][29][30], N-acylenamide reduction [23][24], and carbanion

3D-printed devices for continuous-flow organic chemistry

• Vincenza Dragone,
• Victor Sans,
• Mali H. Rosnes,
• Philip J. Kitson and
• Leroy Cronin

Beilstein J. Org. Chem. 2013, 9, 951–959, doi:10.3762/bjoc.9.109

• ATR-IR flow cell. As a proof of concept, we utilized two types of organic reactions, imine syntheses and imine reductions, to show how different reactor configurations and substrates give different products. Keywords: 3D printing; flow chemistry; flow IR; in-line analysis; imine reduction; imine

• of aldehydes and primary amines. Secondly, two reactors were connected in series to first perform an imine synthesis and then subsequently an imine reduction, with this second setup showing the potential for using the 3D-printed devices as reliable tools in multistep synthesis. This showed that the

• the imine reduction processes. All the characteristics of the devices are summarized in Table 1. The 3D-printed devices were integrated in the flow systems using 1.58 mm outer diameter (OD) polytetrafluoroethylene (PTFE) tubing, with an internal diameter of 0.5 mm and standard connectors made of

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

• studies were also performed in order to elucidate the origin of the stereoselection. Keywords: chiral prolines; imine reduction; Lewis bases; organocatalysis; trichlorosilane; Introduction The reaction with stoichiometric amounts of trichlorosilane in the presence of a chiral catalyst is a well

• ), 130.47 (1C), 128.27 (2C), 127.21 (2C), 59.70 (1C), 50.25 (1C), 28.93 (1C), 25.16 (1C). Imine reduction General procedure: As described in [8]: to a stirred solution of catalyst (0.1–0.3 mol %) in the chosen solvent (2 mL), the imine (1 mmol) was added. The mixture was then cooled to the chosen

Evaluation of a commercial packed bed flow hydrogenator for reaction screening, optimization, and synthesis

• Marian C. Bryan,
• David Wernick,
• Christopher D. Hein,
• James V. Petersen,
• John W. Eschelbach and
• Elizabeth M. Doherty

Beilstein J. Org. Chem. 2011, 7, 1141–1149, doi:10.3762/bjoc.7.132

• ® systems have been used successfully for a variety of reductions; some of the more notable applications including O-debenzylation, CBz-hydrogenolysis, aromatic ring saturation, imine reduction, and enantioselective carbonyl reductions [8][10][11][12][13]. In our hands, the ThalesNano H-Cube® and the H-Cube