Multicomponent reactions driving the discovery and optimization of agents targeting central nervous system pathologies

• Lucía Campos-Prieto,
• Aitor García-Rey,
• Eddy Sotelo and
• Ana Mallo-Abreu

Beilstein J. Org. Chem. 2024, 20, 3151–3173, doi:10.3762/bjoc.20.261

• single step. The oxazepine scaffold can be easily accessed using the Ugi four-component reaction. By modifying this scaffold, the researchers aimed to reduce the hydrogen-bond donating properties. The Passerini reaction, employing bifunctional salicylaldehydes and isocyanides successfully yielded

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• tolerated in this consecutive four-component reaction, as the 1,3,4-thiadiazine synthesis competes with the thiazole synthesis. Salicylaldehydes 14 and 4-hydroxy-6-methyl-2H-pyran-2-one (16) can also be used to produce 1,3-dicarbonyl compounds 18 by Knoevenagel condensation and subsequent cyclization. This

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• -acylhydrazones were synthesized and fully characterized, both in solution and in the solid state. The compounds differ with respect to the carbonyl precursors, i.e., 3-substituted salicylaldehydes with either a methyl or a nitro group. Single crystals of both compounds were isolated from the respective mother

• derived from the same 3,4,5-trimethoxybenzoic acid hydrazide, but differ with respect to the carbonyl precursors: herein, 3-substituted salicylaldehydes (Scheme 1) are used, which assure for a harder donor-atoms set in order to target trivalent metal ions such as aluminum(III), which has been proposed to

• -substituted salicylaldehydes comprising either a methyl or a nitro group. In both cases, XRD confirmed the obtention of the (E)-isomer, in an anti-conformation. An intramolecular H-bond involving the phenolic hydroxy group and the azomethine nitrogen N1 was identified in the solid state, and seems to be

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• Radhakrishnan laboratory reported the Rh-catalyzed oxidative coupling of salicylaldehyde derivatives 151 with diazabicyclic alkenes 130a producing fused chromanone derivatives 152 (Scheme 27) [73]. It was determined alkyl- and methoxy-substituted salicylaldehydes resulted in a minor reduction of yield while

• salicylaldehydes with EWGs failed to react. The authors hypothesized the reaction mechanism begins with the association of the Rh(III) catalyst with the hydroxy group of salicylaldehyde (151a) resulting in a selective cleavage of the aldehyde C–H bond producing the rhodocycle 153 which side-on coordinates with the

Mechanochemical synthesis of unsymmetrical salens for the preparation of Co–salen complexes and their evaluation as catalysts for the synthesis of α-aryloxy alcohols via asymmetric phenolic kinetic resolution of terminal epoxides

• Shengli Zuo,
• Shuxiang Zheng,
• Jianjun Liu and
• Ang Zuo

Beilstein J. Org. Chem. 2022, 18, 1416–1423, doi:10.3762/bjoc.18.147

• The mechanochemical study examined the synthesis of several unsymmetrical salens using monoammonium salts and salicylaldehydes (Scheme 2). Agate mortar and pestle were used for the one-pot two-step mechanochemical reactions (see Supporting Information File 1). Initially, 1,2-diaminocyclohexane or

• ethylenediamine monohydrochlorides were grinded with a half equivalent of 4-diethylamino (Et2N‒), 3,5-dichloro (Cl‒), or 3,5-di-tert-butyl (t-Bu‒) salicylaldehydes (blue moieties in Scheme 2) for 10 minutes. The synthesis of diamine monohydrochlorides and characterization data of mono-imine ammonium salts were

• ), half equivalent of 5-bromo (Br‒), 5-methyl, 4-diethylamino (Et2N‒), 3,5-dichloro (Cl‒), or 3,5-di-tert-butyl (t-Bu‒) salicylaldehydes (red moieties in Scheme 2), and trace methanol, followed by grinding for 20 minutes for the second reaction step to complete, monitored by TLC. A trace amount of

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

• catalyzed by rhodium/diene to afford the 1,2,4-trisubstituted naphthalene framework 8 with complete regio- and stereocontrol (Scheme 1) [62][63]. In 2015, the Nishimura group reported the first iridium-catalyzed addition of salicylaldehydes 14 to bicyclic alkenes 11 (Scheme 1) [64]. Although a variety of

• independently studied the rhodium-catalyzed intermolecular hydroacylation reaction of salicylaldehydes with norbornadiene derivatives. It was found that electron-donating moieties at the C1-position were well tolerated in the hydroacylation reaction giving methyl- (15b), ethyl- (15c), and t-Bu- (15d) adducts in

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• -yl)imino)methyl)phenols 3, was easily synthesized with yields of up to 91% from the reactions involving a series of 2-(R-substituted) 6-amino-4-(trifluoromethyl)quinolines 1 and 4(5)-R1-substituted salicylaldehydes 2 – in which alkyl/aryl/heteroaryl for 2-R-substituents are Me, Ph, 4-MeC6H4, 4-FC6H4

• after recrystallization from ethanol (Scheme 2). In order to evaluate the properties related to the substituents of the portion provided by salicylaldehyde, the same optimized conditions were applied to the reaction of quinoline 1b (R = C6H5) with various salicylaldehydes 2b–e, resulting in four more

• -aminoquinolines and salicylaldehydes and an easy purification methodology with yields of up to 91%. Photophysical experiments with the derivatives exhibited common transitions in these heterocycle units and corroborated the aromatic structures and good fluorescence quantum yield values for all compounds

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• intramolecular coupling of arynes by aldehydes or phenols [21][22][23][24], and Lewis acid-catalyzed cyclization of salicylaldehydes and cyclohexenones or tetralones [25]. Some other new and prominent synthesis methods of xanthenes are the tandem arylation/Friedel–Crafts reaction of o-hydroxy bisbenzylic

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• (difluoromethoxy)arenes, while the reaction with dichlorocarbene gives salicylaldehydes via hydrolysis of an ortho-dichloromethylphenol: the Reimer–Tiemann reaction. The literature, other than this single reference with pentafluorophenol [6], is bereft of references to the capture of heterodihalocarbenes by phenol

Azidophosphonium salt-directed chemoselective synthesis of (E)/(Z)-cinnamyl-1H-triazoles and regiospecific access to bromomethylcoumarins from Morita–Baylis–Hillman adducts

• Soundararajan Karthikeyan,
• Radha Krishnan Shobana,
• Kamarajapurathu Raju Subimol,
• J. Helen Ratna Monica and
• Ayyanoth Karthik Krishna Kumar

Beilstein J. Org. Chem. 2020, 16, 1579–1587, doi:10.3762/bjoc.16.130

• , salicylaldehydes, and methyl- or methoxy-substituted benzaldehydes were also inert under the optimized reaction conditions. Therefore, it is evident that the electronic variation of the substituents on the aromatic moiety of the MBH adducts played a crucial role in determining the outcome of the optimized

• ) also yielded (Z)-methyl 2-(bromomethyl)-3-(furan-2-yl)acrylate (42%) rather than the expected triazole (Scheme 4). Thereby, it was clearly evident that the addition of the individual reagents prevented the formation of complicated triazoles. Interestingly, the MBH adducts derived from salicylaldehydes

Mn-mediated sequential three-component domino Knoevenagel/cyclization/Michael addition/oxidative cyclization reaction towards annulated imidazo[1,2-a]pyridines

• Olga A. Storozhenko,
• Alexey A. Festa,
• Delphine R. Bella Ndoutoume,
• Alexander V. Aksenov,
• Alexey V. Varlamov and
• Leonid G. Voskressensky

Beilstein J. Org. Chem. 2018, 14, 3078–3087, doi:10.3762/bjoc.14.287

• , complicated by the need of an oxidant to fulfil the final aromatization. Following our interest in domino [42][43] and MCR chemistry [44][45] and taking an advantage of 2-iminochromene reactivity, herein we report a sequential three-component domino reaction of salicylaldehydes 2 and N-(cyanomethyl)pyridinium

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• .14.246 Abstract A new metal-free one-pot three-component procedure towards fully substituted triazolochromenes has been developed, starting from commercially available materials. Salicylaldehydes and nitroalkenes were reacted under solvent-free conditions, followed by a 1,3-dipolar cycloaddition of the

• was carried out for several salicylaldehydes and gave a clear improvement in the yield of the corresponding triazolochromenes and consequently showed to be a viable alternative for solid salicylaldehydes. Keywords: ball milling; multicomponent reaction; 3-nitro-2H-chromene; one-pot synthesis; 1,2,3

• assembly of triazole-fused (hetero)cycles [24][33][34][35][36][37][38][39][40][41][42], we opted to develop a new one-pot two-step three-component reaction starting from salicylaldehydes, nitroalkenes and organic azides, without isolation of the intermediate 3-nitrochromenes, in a regioselective manner and

Recent developments in the asymmetric Reformatsky-type reaction

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 325–344, doi:10.3762/bjoc.14.21

• reported the synthesis of novel chiral tridentate ligands from the reaction between (1R,2S)-2-amino-1,2-diphenylethanol and substituted salicylaldehydes [43]. These chiral 1,2-amino alcohols were further investigated as ligands in the enantioselective Reformatsky reaction of aldehydes with ethyl

Effect of the ortho-hydroxy group of salicylaldehyde in the A³ coupling reaction: A metal-catalyst-free synthesis of propargylamine

• Sujit Ghosh,
• Kinkar Biswas,
• Suchandra Bhattacharya,
• Pranab Ghosh and
• Basudeb Basu

Beilstein J. Org. Chem. 2017, 13, 552–557, doi:10.3762/bjoc.13.53

• interest of synthetic and medicinal chemists. Synthesis of various propargylamines from various salicylaldehydes under metal-catalyst-free conditions. Representative examples of bioactive compounds bearing a propargylamine moiety and synthesis of various N-heterocycles from propargylamine-containing

(Z)-Selective Takai olefination of salicylaldehydes

• Stephen M. Geddis,
• Caroline E. Hagerman,
• Warren R. J. D. Galloway,
• Hannah F. Sore,
• Jonathan M. Goodman and
• David R. Spring

Beilstein J. Org. Chem. 2017, 13, 323–328, doi:10.3762/bjoc.13.35

• led to the identification of key factors responsible for this surprising inversion of selectivity, and enabled the development of a modified mechanistic model to rationalise these observations. Keywords: alkenyl iodides; salicylaldehydes; stereoselectivity; Takai olefination; transition state

• ortho-OH results in a higher (Z)-selectivity than for either substituent in isolation. In order to further investigate this cooperative effect, the (E):(Z)-product ratios were determined for various substituted salicylaldehydes (with ortho-OH substitution already demonstrated as optimum for favouring

• to the expected (E)-product (See Supporting Information File 1). This precludes the possibility that the salicylaldehydes are functioning as ligands for chromium. In light of this and the above observations, we propose an alternative pathway by which the reaction may proceed in order to favour the (Z

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• attention from organic chemists. The best procedure for the preparation of these compounds involves a one-pot three-component reaction between salicylaldehydes 157, malononitrile (145) and trialkyl phosphite that was first reported by Perumal et al. (Scheme 34) [57]. The desired (2-amino-3-cyano-4H-chromen

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• was used as the OH-reagent along with 1,3-ketoesters. However, the reaction with 1,3-cyclohexanedione gave products in low yields (19–26%). The coupling of a number of substituted salicylaldehydes with formamides was performed; the aldehyde group, which is prone to oxidation, remaining intact [157

The unexpected influence of aryl substituents in N-aryl-3-oxobutanamides on the behavior of their multicomponent reactions with 5-amino-3-methylisoxazole and salicylaldehyde

• Volodymyr V. Tkachenko,
• Elena A. Muravyova,
• Sergey M. Desenko,
• Oleg V. Shishkin,
• Svetlana V. Shishkina,
• Dmytro O. Sysoiev,
• Thomas J. J. Müller and
• Valentin A. Chebanov

Beilstein J. Org. Chem. 2014, 10, 3019–3030, doi:10.3762/bjoc.10.320

• salicylaldehydes in a Biginelli-like three-component condensation, two alternative outcomes were observed by Gorobets et al. [18]. When the condensation with acetone was performed in methanol with catalytic amounts of HCl under reflux conditions, a tetrahydrotriazolo[1,5-a]pyrimidine derivative was obtained, while

Silver and gold-catalyzed multicomponent reactions

• Giorgio Abbiati and
• Elisabetta Rossi

Beilstein J. Org. Chem. 2014, 10, 481–513, doi:10.3762/bjoc.10.46

Diversity-oriented synthesis of dihydrobenzoxazepinones by coupling the Ugi multicomponent reaction with a Mitsunobu cyclization

• Lisa Moni,
• Luca Banfi,
• Andrea Basso,
• Alice Brambilla and
• Renata Riva

Beilstein J. Org. Chem. 2014, 10, 209–212, doi:10.3762/bjoc.10.16

• ]. On the other hand, various ortho-hydroxybenzyl alcohols are on the market or can be easily prepared from the corresponding salicylaldehydes or salicylic acids. Thus we decided to set up a general and efficient strategy to access the desired amines, through conversion of the benzyl alcohols into

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• , pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to

• biological and pharmaceutical applications. In continuation of our interest in the cycloisomerization of alkynols and alkynamines for the synthesis of various heterocycles [17][18][19][20][21][22], we herein report the synthesis of coumarins from salicylaldehydes by a Cu-catalyzed exclusive 6-endo-dig

• salicylaldehydes. As is apparent from Table 2, the reaction is highly versatile, working efficiently with both electron-rich and -poor substrates. Substrates 1b–h with various alkyl substituents produced the corresponding coumarins 2b–h in 50–82% yield. A slight reduction in yield was observed in the cases of

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• -, methyl- and nitro-substituted salicylaldehydes. The nitro- and 3,5-dibromo-substituted salicylaldehydes reacted with 18 to give the lowest yields of 60–70% while the other substituted salicylaldehydes reacted to give corresponding chromane derivatives in yields comparable to those achieved when 5 was

• -diethylamino- and 5-bromo-3-methoxy-substituted salicylaldehydes gave corresponding 2-iminochromene derivatives in 86–100% yields, while the lowest yield of 62% was achieved when 3,4-dihydroxysalicylaldehyde was used. Further studies by Costa and co-workers revealed that the reaction of salicyldehyde (5) with

• the reaction of malononitrile derivative 35 as an enolate equivalent and salicylaldehydes 5 to give 2-iminochromenes 36 in good yields [25]. No Michael addition product was observed. 2-hydroxy-5-methoxybenzaldehyde (5a) gave product 36a in a higher yield of 81% compared to salicylaldehyde (5), which

Organocatalytic tandem Michael addition reactions: A powerful access to the enantioselective synthesis of functionalized chromenes, thiochromenes and 1,2-dihydroquinolines

• Chittaranjan Bhanja,
• Satyaban Jena,
• Sabita Nayak and
• Seetaram Mohapatra

Beilstein J. Org. Chem. 2012, 8, 1668–1694, doi:10.3762/bjoc.8.191

• 2006, using diarylprolinolether as an effective organocatalyst. This method involved an oxa-Michael attack of salicylaldehydes 1 on the α,β-unsaturated aldehydes 2 activated through an iminium ion formation with the catalyst Ib, followed by an intramolecular aldol reaction and the subsequent water

• , Córdova et al. [42][43] and subsequently Wang et al. [44] independently reported similar oxa-Michael/aldol reactions by means of the same iminium-ion activation strategies but with improved yields and enantioselectivities. Córdova et al. reported the tandem reaction of salicylaldehydes 1 and α,β

• sieves (4 Å) in the reaction (Scheme 2). Wang et al. [44] investigated the same tandem reaction of salicylaldehydes 1 and α,β-unsaturated aldehydes 2 employing TES-protected diphenylprolinol Ie as organocatalyst with high catalyst loading (30 mol %). With benzoic acid as cocatalyst and dichloroethane as

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• ’-hydroxycinnamic esters 3, which were readily obtained by reaction of substituted salicylaldehydes with methyl triphenylphosphoranylidene acetate (Ph3P=CHCO2Me) [16][28]. They were cyclized to the corresponding substituted coumarins 4 under the optimized conditions, involving 20 mol % of n-Bu3P as the catalyst in

Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

• Dieter Enders,
• Jeanne Fronert,
• Tom Bisschops and
• Florian Boeck

Beilstein J. Org. Chem. 2012, 8, 1112–1117, doi:10.3762/bjoc.8.123

• intramolecular aldol reaction of O-acetonyl-salicylaldehydes was described by our research group (Scheme 3) [10]. We envisaged that this 5-enolexo aldolization could be utilized to construct the 1,3-diol moiety of smyrindiol, if a coumarin derivative of the O-acetonyl-salicylaldehyde were to be used. The

• /lactonization sequence opens a new efficient and flexible entry to the coumarin core of other natural products. Furocoumarins. Synthesis of smyrindiol (1) by Grande et al. Synthesis of smyrindiol by Snider et al. Proline-catalyzed intramolecular aldol reaction of O-acetonyl-salicylaldehydes. First