Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• β/α mixture was obtained when 2a was reacted with neat bromotrimethylsilane at room temperature. Bromination of 2b yielded a 10:1 β/α mixture of the anomeric bromide 7b [27]. The reaction between Nam (1a) and the bromide 7a was carried out in liquid SO2 and proceeded in high yields with the

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• , m/z): [M + Na]+ calcd for C51H63N3NaO12, 932.4304; found, 932.4302; IR (neat) : 3661, 2349, 1716, 1495, 1163, 1044, 755 cm−1. General procedure for the mono- and dipeptide products 11, 12 and 13 Negishi coupling product 10 was dissolved in dichloromethane/trifluoroacetic acid (CH2Cl2/TFA 1:1) and

• , 127.6, 125.0, 53.6, 52.6, 37.7 ppm; HRMS–ESI (Q-Tof, m/z): [M + H]+ calcd for C51H46N3O9S3, 940.2391; found, 940.2392; IR (neat) : 3769, 3327, 2932, 1664, 1169, 759 cm−1. Dipeptide 12 Colorless solid; yield 73% (97 mg, starting from 100 mg of 10); Rf = 0.59 (6:4 ethyl acetate/petroleum ether); mp <230

• , J = 6.8 Hz, 9H), 0.87 (d, J = 4.0 Hz, 9H) ppm; 13C NMR (100 MHz, CDCl3) δ 171.8, 171.5, 155.9, 141.9, 139.9, 135.3, 129.8, 127.5, 124.9, 79.9, 60.0, 53.2, 52.4, 37.8, 31.0, 28.4, 19.3, 17.8 ppm; HRMS–ESI (Q-Tof, m/z): [M + Na]+ calcd for C66H90N6NaO15, 1229.6356; found, 1229.6359; IR (neat) : 3342

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• was used as solvent with an 8.9% increase at 420 min. This affected the other performance indicators, i.e., PMPs, S, TON and TOF; lower values than the neat reactions were obtained. The results suggest that no significant solvent effect appears to exist .However, the increase in SMPs (associated with

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• of N,N-dimethallyl-N-tosylamide (93) only 2 mol % of 85 were required to produce 54% of the tetrasubstituted tosylamide 94 within 3 h (Scheme 10). Moreover, catalyst 85 was quite efficient under neat conditions for the self metathesis of allylbenzene (13), showing no trace of isomerized byproducts

• saturated NHC ligand containing a N-substituted cyclododecyl side chain was first evaluated at 50 ppm loading in the self metathesis of 1-octene (96), at 50 °C under neat conditions, in comparison to symmetrical benchmark second-generation ruthenium catalysts IndII-SIMes, IndII-IMes, GII-SIMes and HGII

• distribution with no isomerization was observed without the use of any additive even after 24 h of reaction performed at 50 °C under neat conditions. N-Alkyl substituents possessing functionalities or heteroatoms In 2001, the Fürstner group reported on phosphine-containing ruthenium complexes having

Cross metathesis-mediated synthesis of hydroxamic acid derivatives

• Shital Kumar Chattopadhyay,
• Subhankar Ghosh and
• Suman Sil

Beilstein J. Org. Chem. 2018, 14, 3070–3075, doi:10.3762/bjoc.14.285

• reaction mixture was allowed to cool to room temperature and then concentrated in vacuo. The residue was purified by column chromatography on silica gel (hexane/ethyl acetate 60:40) to provide the CM product (E)-N-benzyloxy)undec-2-enamide (6a, 133 mg, 81%) as a colourless viscous liquid. IR (neat): 3183

• 85 °C; IR (neat): 3259, 3058, 2956, 1663, 1624 cm−1; 1H NMR (400 MHz, DMSO-d6) δ 10.52 (s, 1H, NH), 8.93 (brs, 1H, OH), 1.92 (t, J = 7.2 Hz, 2H, C2-H), 1.44 (m, 2H, C3-H), 1.19 (s, 14H, 7× CH2), 0.81 (t, J = 6.8 Hz, 3H, C11-H); 13C NMR (100 MHz, DMSO-d6) δ 170.4 (CO), 32.6 (C2), 31.6 (C3), 29.3 (CH2

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• –30 °C under argon gas cover during the addition of n-BuLi (1.05 mmol) in hexane (0.47 mL). The created LDA (up to 1.05 mmol) solution was treated with the solid nitrile 1 (200 mg, 0.95 mmol) and stirred further at rt till 1 was completely dissolved, whereupon the carbonyl compound (1.24 mmol, neat or

Stereodivergent approach in the protected glycal synthesis of L-vancosamine, L-saccharosamine, L-daunosamine and L-ristosamine involving a ring-closing metathesis step

• Pierre-Antoine Nocquet,
• Aurélie Macé,
• Frédéric Legros,
• Jacques Lebreton,
• Gilles Dujardin,
• Sylvain Collet,
• Arnaud Martel,
• Bertrand Carboni and
• François Carreaux

Beilstein J. Org. Chem. 2018, 14, 2949–2955, doi:10.3762/bjoc.14.274

• ) [35]. Indeed, the reaction of achiral pinacol (Z)-crotylboronate with 5 under neat conditions at room temperature gave a good level of diastereoselectivity for the hitherto unreported 3,4-syn-2,3-anti product 12b [36][37][38][39]. The syn relationship between C3 and C4 is controlled by the (Z

MoO₃ on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

• Hynek Balcar,
• Martin Kubů,
• Naděžda Žilková and
• Mariya Shamzhy

Beilstein J. Org. Chem. 2018, 14, 2931–2939, doi:10.3762/bjoc.14.272

• MoO3 and/or MoO2(acac)2 on MWW zeolites (MCM-22, delaminated MCM-56) and on two-dimensional MFI (all in NH4+ form). The catalysts‘ activities were tested in the metathesis of neat 1-octene (as an example of a longer chain olefin) at 40 °C. Catalysts with 6 wt % or 5 wt % of Mo were used. The acidic

• supported MoO3 and/or MoO2(acac)2 on (i) 2D-MFI (and ordinary HZSM-5 for comparison) and similarly on (ii) MCM-56 and its 3D analogue MCM-22 (both in NH4+ form) and examined their activity in the metathesis of neat 1-octene (Scheme 1) under ambient pressure and 40 °C. According to our best knowledge, none

• molybdenum oxide metathesis catalysts. The catalysts, prepared by thermal spreading of MoO3 and/or MoO2(acac)2 on these supports in NH4+ forms (6 wt % and/or 5 wt % of Mo) were tested in neat 1-octene metathesis under mild conditions (batch reactor, atmospheric pressure, 40 °C). The catalyst activity

Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

• Pavel Yanev and
• Plamen Angelov

Beilstein J. Org. Chem. 2018, 14, 2602–2606, doi:10.3762/bjoc.14.238

• behaviour. Domino fragmentation of α-aminoacyl intermediates 3 to N-protected γ-amino-β-ketoamides 5 Initially we tried a procedure developed earlier by us for simpler β-keto amides (30 min in neat TFA, then aqueous NaOAc) [22]. In contrast to the preparation of non-functionalised β-keto amides, here these

• mainly on the duration of the exposure of 3 to acid. Given enough time, the treatment in neat or diluted TFA led to a complete transformation of 3a–f into 6 without formation of the desired β-keto amides 5a–f at all. On the contrary – when the deprotection was carried out for 5 min in neat TFA, the

• favourable 5-exo-trig process, leading eventually to the pyrrolin-4-ones 6. This hypothesis is strongly supported by the behaviour of analogues 9 in which the auxiliary amino group is absent (Scheme 5). Under identical conditions (neat TFA, rt) compounds 9 do not react even after 12 hours. A reaction occurs

Design and synthesis of C₃-symmetric molecules bearing propellane moieties via cyclotrimerization and a ring-closing metathesis sequence

• Sambasivarao Kotha,
• Saidulu Todeti and
• Vikas R. Aswar

Beilstein J. Org. Chem. 2018, 14, 2537–2544, doi:10.3762/bjoc.14.230

• , 6H), 6.28 (s, 6H), 3.51–3.44 (m, 12H), 1.79 (d, J = 8.8 Hz, 3H), 1.61 (d, J = 8.8 Hz, 3H) ppm; 13C NMR (125 MHz, CDCl3) δ 177.0, 141.8, 141.3, 134.8, 131.4, 128.2, 127.2, 125.7, 52.4, 46.0, 45.7 ppm; HRMS (ESI, Q-ToF) m/z: [M + H]+ calcd for C51H40N3O6, 790.2912; found, 790.2918; IR (neat) max: 2918

• , 175.4, 136.7, 136.2, 136.1, 129.2, 126.5, 116.3, 49.1, 46.4, 35.4, 26.8 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C19H19NO3·Na, 332.1257; found, 332.1254; IR (neat) max: 2325, 1671, 1263, 746 cm−1. Synthesis of trimerized compound 12 Based on the earlier procedure of trimerization, compound 13

• , 131.4, 128.1, 126.9, 125.6, 116.1, 49.1, 46.3, 35.5 ppm; HRMS (ESI, Q-ToF) m/z: [M + Na]+ calcd for C57H51N3O6·Na, 896.3670; found; 896.3678; IR (neat) max: 2342, 1709, 1512, 1183, 919, 736 cm−1. Synthesis of trimerized product 19 Based on the earlier procedure of trimerization, compound 18 (500 mg

Quinolines from the cyclocondensation of isatoic anhydride with ethyl acetoacetate: preparation of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate and derivatives

• Nicholas G. Jentsch,
• Jared D. Hume,
• Emily B. Crull,
• Samer M. Beauti,
• Amy H. Pham,
• Julie A. Pigza,
• Jacques J. Kessl and
• Matthew G. Donahue

Beilstein J. Org. Chem. 2018, 14, 2529–2536, doi:10.3762/bjoc.14.229

• the undesired quinoline 12. We then turned to a functional group transformation of the ethyl ester at the 3-position to address the acetic acid sidechain problem (Scheme 7). First, the 4-hydroxy group in quinoline 10f was substituted for chlorine with neat phosphorus oxychloride to afford chloride 14

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• alkynes with azobenzenes 1 to synthesize dialkenated products 2 (Scheme 4) [32]. The reaction resulted in an anti-addition of the C–H bond with alkynes using the cobalt(I) catalysts CoH(N2)(PPh3)3 or CoH3(PPh3)3 under neat reaction conditions. After fifteen years, Yoshikai and co-workers developed a low

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• = 13.2, 11.2 Hz, 1H), 2.11–2.04 (m, 1H), 1.50 (s, 3H, Me), 1.47 (s, 3H, Me), 1.37 (s, 3H, Me); 13C NMR (100 MHz, CDCl3) δ 203.4 (C=O), 171.0, 167.7, 84.5, 58.0, 55.6, 52.8, 44.9, 35.1, 29.3, 22.3, 18.7; IR (neat): 2900, 1760, 1740, 1440 cm−1; HRMS (m/z): [M]+ calcd for C12H16O5, 240.0998; found, 240.1001

• , Me), 1.49 (s, 3H, Me), 1.36 (s, 3H, Me); 13C NMR (100 MHz, CDCl3) δ 201.4 (C=O), 169.3, 168.4, 80.2, 59.2, 56.4, 53.5, 44.4, 36.5, 28.7, 22.6, 19.8, 18.7; IR (neat): 2900, 1760, 1740, 1440 cm−1; HRMS (m/z): [M]+ calcd for C13H18O5, 254.1154; found, 254.1155. Methyl 5-allyl-1,1-dimethyl-3,4

• –2.30 (m, 1H), 2.25–2.20 (m, 1H), 1.50 (s, 3H, Me), 1.44 (s, 3H, Me); 13C NMR (125 MHz, CDCl3) δ 202.6, 169.9, 167.8, 131.8, 120.2, 84.8, 61.8, 56.2, 53.0, 44.5, 37.3, 31.2, 29.4, 22.3; IR (neat): 2900, 1760, 1720, 1420 cm−1; HRMS (m/z): [M]+ calcd for C14H18O5, 266.1154; found, 266.1150. Methyl 5-allyl

Assessing the possibilities of designing a unified multistep continuous flow synthesis platform

• Mrityunjay K. Sharma,
• Roopashri B. Acharya,
• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2018, 14, 1917–1936, doi:10.3762/bjoc.14.166

• covered here from the case studies, where two reactants 2-dimethylaminoethanol and neat chlorodiphenylmethan is being pumped from P1 and P2 to reactor R1 where it is getting heated at a temperature of 180 °C at a pressure of 1.7 MPa. The molten salt which comes out of reactor R1 is then treated with

Water-soluble SNS cationic palladium(II) complexes and their Suzuki–Miyaura cross-coupling reactions in aqueous medium

• Alphonse Fiebor,
• Richard Tia,
• Banothile C. E. Makhubela and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1859–1870, doi:10.3762/bjoc.14.160

• solvents in the presence of an excess of base [1][2][3]. With the drive for the development of environmentally friendly and low cost protocols, a number of methodologies for the Suzuki–Miyaura reaction under aqueous conditions or in neat water have been reported [4][5][6]. This has been achieved via

• investigation of their catalytic activity in the aqueous Suzuki–Miyaura coupling reaction. Herein, we report the synthesis of the SNS Pd(II) pincer complexes and their interesting catalytic activities in the Suzuki–Miyaura cross coupling reactions in neat water. Results and Discussion Our study commenced with

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• quantitative yields and generally very high enantioselectivities [42][43]. Using the chiral bipyridine ligand 50 and Sc(OSO3C12H25)3 as a catalyst, the asymmetric thiolysis of meso-epoxides 51 in neat water was achieved to provide the corresponding β-hydroxy sulfides in moderate to good yields with high

• reported the use of β-cyclodextrin as a catalyst for the hydroxysulfurization of alkenes with thiophenols in neat water under atmospheric oxygen as shown in Scheme 26 [63]. As opposed to the usual acid-base type of catalysis, β-cyclodextrin having hydrophobic cavities catalyze reactions via formation of

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• reported in literature (3.18 ± 0.01), 2 is still in its anionic dissociated form at pH 4.4. Similarly, a neat increase of the sequestration percentage occurs, on increasing the pH from 6.7 to 10.7, for the basic diamine derivative 5 (pKBH+ = 10.19 ± 0.01), which passes from its cationic to its neutral form

Metal-free formal synthesis of phenoxazine

• Gabriella Kervefors,
• Antonia Becker,
• Chandan Dey and
• Berit Olofsson

Beilstein J. Org. Chem. 2018, 14, 1491–1497, doi:10.3762/bjoc.14.126

• the neat crude product at rt, along with 52% of 4-iodoanisol (see Supporting Information File 1). This observation is in line with a ligand-coupling (LC) mechanism [30][35][36] where the observed byproduct could be the T-shaped intermediate 9 or the corresponding 4-coordinated species with two

• room temperature and could be converted to the arylated products upon heating. The reactivity of 9 is unusual, as it proved stable to neutral work-up with brine, formed product 3 upon longer reaction time or rt storage in CDCl3 or neat, but decomposed to starting materials upon work-up with sat

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• fabricated OLEDs using phosphor 13 as emitting layer was ITO (100 nm)/TAPC (80 nm)/4,4’,4’’-tri(9-carbazoyl)triphenylamine (TCTA) (10 nm)/Pt(fppz)2 neat (30 nm)/1,3-bis(3,5-di(pyridin-3-yl)phenyl)benzene (BMPYPB) (15 nm)/BMPYPB:1 wt % Rb2CO3 (40 nm)/Al (100 nm). These devices exhibited an outstanding EQE

• phenyl ring. As the parent complex 23a, excimer formation via metal–metal interactions was observed for both derivatives at high concentrations or in neat films. Nevertheless, the increased conjugation within the chromophoric ligand led to a lower emission energy, which fell into the NIR region. The

• and high thermal stability. Unfortunately, going from dilute solution to neat solid-state samples, PLQY values dramatically dropped to values as low as 0.10–0.02 that might point to strong intermolecular interaction and TTA phenomena. The tendency toward aggregation for complex 44 and 46 in condensed

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• derivatives, Sikchi and Hultin contrived an attritor-type mill (Figure 1c) to facilitate the use of neat reagents and vent CO2 (closed vessels were reported to break) [19]. Efficient gram-scale Boc protection of amine and carboxylic acid functions was thereby effected (Scheme 3). This chemistry was further

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• energy and reactant [53][54][55]. Thus, the effect of the grinding auxiliaries was also investigated. The results were shown in Table 2. Compared to using silica gel as grinding auxiliary, the reaction under neat conditions gave only 10% yield of 3aa, but the dehalogenation was depressed (Table 2, entry

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• ; nanoreactors; micelles; polymersomes; Introduction It is widely acknowledged that “the best solvent is no solvent”; however, running a reaction under neat conditions is very challenging from the points of view of mass transfer and temperature gradients [1][2]. Therefore, sustainable chemical technologies are

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• + Na]+ calcd for C18H18B2N2, 307.1548; found, 307.1561; IR (neat): 3124, 3041, 2965, 2918, 2829, 1581, 1468, 1425, 1310, 1286, 1276, 1153, 1113, 997, 950, 889, 754, 713, 610, 575. IEDDA reactions catalyzed by the air-stable bidentate Lewis acid catalyst B General procedure A for IEDDA reactions of

High-yielding continuous-flow synthesis of antimalarial drug hydroxychloroquine

• Eric Yu,
• Hari P. R. Mangunuru,
• Nakul S. Telang,
• Caleb J. Kong,
• Jenson Verghese,
• Stanley E. Gilliland III,
• Saeed Ahmad,
• Raymond N. Dominey and
• B. Frank Gupton

Beilstein J. Org. Chem. 2018, 14, 583–592, doi:10.3762/bjoc.14.45

• in a continuous stirred tank reactor (CSTR). The last step requires the reaction of 12 with 4,7-dichloroquinoline (13) which when used neat takes 24–48 hours at 120–140 °C to give 75–80% yield of HCQ (1) [37]. We have found that this step can be accelerated by employing K2CO3/triethylamine, to

• Information File 1) 10 reacts rapidly and cleanly with 7 under flow conditions to give 6 in high yield (>80%). Furthermore, we have developed and optimized a continuous synthesis of 10 (Table 1), wherein hydroiodic acid is reacted with neat 3-acetyldihydrofuran-2(3H)-one (8) to provide a rapid route to 10

• of 68% for compound 12. With an optimized continuous process for producing the key intermediate 12 in-hand the reaction conditions for the conversion of 12 to HCQ (1) were examined. In the commercial process this step is carried out in batch under neat reactant conditions and requires a relatively

Copper-catalyzed asymmetric methylation of fluoroalkylated pyruvates with dimethylzinc

• Kohsuke Aikawa,
• Kohei Yabuuchi,
• Kota Torii and
• Koichi Mikami

Beilstein J. Org. Chem. 2018, 14, 576–582, doi:10.3762/bjoc.14.44

• (t, 3H, J = 7.0 Hz); 13C NMR (75 MHz, CDCl3) δ 164.3, 162.3, 151.1, 134.0, 131.2, 123.7, 122.7 (q, J C-F = 282.9 Hz), 80.7 (q, J C-F = 30.4 Hz), 63.2, 16.6, 13.8; 19F NMR (282 MHz, CDCl3) δ −78.4 (s, 3F); HRMS (APCI-TOF): [M]−· calcd for C13H12F3NO6, 335.0617; found, 335.0623; FTIR (neat, cm−1) 784

• = 289.90 Hz, JF-H = 56.4 Hz, 1F); HRMS (APCI-TOF): [M + Na]+ calcd for C13H14F2NaO4, 295.0758; found, 295.0761; FTIR (neat, cm−1) 1026, 1093, 1114, 1216, 1279, 1388, 1452, 1602, 1730, 1747, 2938, 2985, 3021; [α]D25 −7.47 (c 1.01, CHCl3); HPLC (column, CHIRALCEL OJ-3, hexane/2-propanol 99:1, flow rate 0.6

• = 288.2 Hz, 1F), −123.882 (s, 2F); HRMS (APCI-TOF): [M]−· calcd for C15H12F7NO6, 435.0553; found, 435.0547; FTIR (neat, cm−1) 1090, 1140, 1200, 1233, 1349, 1387, 1534, 1609, 1744, 1761, 2942, 2988, 3059; [α]D25 −22.60 (c 0.94, CHCl3); HPLC (column, CHIRALCEL OJ-3, hexane/2-propanol 99:1, flow rate 0.6 mL