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

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• amine derivatives (e.g., hydrochloride salt, mandelic acid salt, phthalimide, ketopinic acid amide, salicylaldehyde imine, p-toluenesulfonamide, acetamide, etc.), all attempts to separate the resulting isomers (which were oils) were similarly unsuccessful. Seeking an alternative to column chromatography

Oxa-Michael-initiated cascade reactions of levoglucosenone

• Julian Klepp,
• Thomas Bousfield,
• Hugh Cummins,
• Sarah V. A.-M. Legendre,
• Jason E. Camp and
• Ben W. Greatrex

Beilstein J. Org. Chem. 2022, 18, 1457–1462, doi:10.3762/bjoc.18.151

• ]. The reaction is interesting as both furfural and 1 are present along with water in crude biomass pyrolysates, and so the reaction could affect yields of 1 [3][17][18]. Samet and co-workers have reported a similar condensation of 1 with salicylaldehyde resulting in chiral chromene derivative 4 [19][20

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

• due to the strong electron-withdrawing effect of bromine, enhancing the electrophilic property of bromo-substituted salicylaldehyde. Because of the poor solubility in the eluent, the yield of dichloro-containing 1c (88%) was lower than 1a after isolating by column chromatography. This was also found

• monohydrochlorides and salicylaldehydes (blue in Scheme 2) took 1 hour for reaction completion. After adding another salicylaldehyde (red in Scheme 2), Et3N, and methanol, the second reaction step was completed in an additional hour, monitored by TLC. Yields of unsymmetrical salens using grinding and ball milling

• –salen catalysts. Synthetic approach to our unsymmetrical Co–salen catalyst 2f for the asymmetric synthesis of α-aryloxy alcohols. Mechanochemical one-pot two-step synthesis of unsymmetrical salens 1a–h. Reaction conditions: salicylaldehyde (1 mmol) and diamine unilateral hydrochloride salt (2 mmol) were

Synthesis of odorants in flow and their applications in perfumery

• Merlin Kleoff,
• Paul Kiler and
• Philipp Heretsch

Beilstein J. Org. Chem. 2022, 18, 754–768, doi:10.3762/bjoc.18.76

• ) following the Perkin synthesis (Scheme 10) [42]. Salicylaldehyde (44) is mixed with a solution of potassium acetate and acetic acid in acetic anhydride. The reaction mixture is pumped through two separated tube reactors at 150 °C and 240 °C, respectively, proceeding with a combined residence time of 22.5

• min. The authors propose that the reaction does not follow the mechanism of the Perkin process but proceeds via acylation of salicylaldehyde (44) to intermediate 45, which forms coumarin (46) in an intramolecular aldol cyclization. Therefore, O-acylation of salicylaldehyde (44) is completed at 150 °C

• = mass flow controller. Synthesis of thymol (41) from m-cresol (39) and isopropyl alcohol via Fries-type rearrangement of ether 40. Preparation of coumarin (46) by reaction of salicylaldehyde (44) with potassium acetate, acetic acid, and acetic anhydride at elevated temperature in two separated tube

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

• iridium-catalyzed hydroacylation of C1-substituted oxabenzonorbornadienes with salicylaldehyde is reported. Utilizing commercially available [Ir(COD)Cl]2 in the presence of 5 M KOH in dioxane at 65 °C, provided a variety of hydroacylated bicyclic adducts in up to a 95% yield with complete stereo- and

• effects of C1-substitution on the iridium-catalyzed hydroacylation reactions of unsymmetrical OBDs with salicylaldehyde. To further understand the observed regioselectivity, an in-depth investigation into the reaction mechanism of the iridium-catalyzed hydroacylation reaction was carried out by preforming

• reaction with C1-substituted methyl OBD (MeOBD) with salicylaldehyde catalyzed by [Ir(COD)OH]2 was chosen as the model reaction. As the reaction is in the presence of 5 M KOH, the potassium salt of salicylaldehyde was used rather than the protonated species for all calculations. Likewise, [Ir(COD)OH]2, and

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

• trifluoromethylated hybrid system comprising the Schiff base scaffolds from some 6-aminoquinolines and salicylaldehyde derivatives in order to analyze and evaluate their photophysical, photostability, and antioxidant properties for possible future applications in the pharmacological areas or materials sciences

• literature by our research group [14]. With the quinolines 1a–f at hands we initially selected quinoline 1b and salicylaldehyde (2a) to optimize the reaction conditions leading to Schiff bases 3. Hence, the reaction solvent and molar ratio between the precursors were evaluated. The reactions were carried out

• ). Based on these results, we selected acetonitrile as the best solvent for further optimization. When changing the molar ratio of the reactants to a 1:2 molar ratio of quinoline 1b and salicylaldehyde (2a), the yield of the desired product 3ba increased to 90%. The best result was obtained when quinoline

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• orange color developed by phenol itself faded, and salicylaldehyde was formed [6]. The mechanism of the Guareschi reaction was clarified only in the 70s of the past century, and the relationship to the mechanism of the Reimer–Tiemann reaction became obvious (Scheme 2) [5]. Thus, dichlorocarbene generated

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

• synthesis of coumarin (90) was also reported, which involved an intramolecular aldol-type condensation of the acetylated intermediate 89 derived from salicylaldehyde (88, Scheme 18) [125]. The initial O-acetylation step was telescoped directly into the next reactor; the two-step process gave an overall

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• imidodiphosphoric acid-catalyzed asymmetric Prins cyclization with salicylaldehyde 316 and 3-methylbut-3-en-1-ol (317) to afford 4-methylenetetrahydropyrans 318 with high enantioselectivity (Scheme 73) [115]. A chiral bis-BINOL-based imidophosphoric acid 319 was efficient in this reaction, and the extreme bulkiness

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• ). Cyclohexanol (26) was observed only once in C. marinus, and aromatic compounds included benzyl alcohol (27), benzaldehyde (28) and salicylaldehyde (29), acetophenone (30) and o-aminoacetophenone (31), 2-phenylethanol (32), and phenylacetone (33). 6-Methylhept-5-en-2-one (34) was detected in all strains, while

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• having a free amino and strong donor-acceptor groups and a pyridin-2-yl moiety were synthesized by the base-catalyzed condensation of 2 with different aldehyde derivatives in ethanol, as depicted in Scheme 1. Further reactions of the dyes 3–7 with salicylaldehyde under basic conditions resulted in the

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• corresponding products 3p and 3q in good isolated yields within a short period of time (15 min and 13 min, respectively, Table 5, entries 16 and 17). However, salicylaldehyde (2h) afforded the unexpected product 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))diphenol (3h, bisimine I

• /-thiones 7, and iii) 2-amino-4-(hetero)aryl-3,5-dicarbonitrile-6-sulfanylpyridines 11 under ultrasound irradiation. Unexpected formation of the bisimine I, 3h, from o-phenylenediamine (1) and salicylaldehyde (2h). Chemical composition of the NDL catalyst. LOI: loss of ignition. Optimization of the reaction

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

• were inert to triazolations, surprisingly affords bromomethylcoumarin in the presence of AzPS and HBr. The reaction was optimized using salicylaldehyde (1 equiv) in the presence of AzPS (2 equiv) and HBr (2.0 equiv). The reaction afforded 6-(bromomethyl)coumarin (4a) in a yield of 78% (Table 2, entry 3

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• , proved to be completely inactive as the photosensitizer. Also, no reaction was observed when salicylaldehyde (68) was employed as a photosensitizer, despite of a triplet state energy of ≈70 kcal/mol, most probably due to an internal hydrogen bond (Scheme 16). As mentioned before, in the section on the

• photosensitizers. Salicylaldehyde (68) forms an internal hydrogen bond. Olefin isomerization via energy transfer from a carbonyl compound. Mechanistic pathways for the Paterno–Büchi reaction. Isomeric oxetanes formed after photochemical addition of aryl aldehydes to 2-butenes. Rotation of the C3–C4 bond of the

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• (3CR) developed by Barluenga et al. [35] to steroids. The original Barluenga’s 3CR comprises the reaction of salicylaldehyde with an alkyl orthoformate and 4-pentyn-1-ol to obtain a 4-alkylchroman spiroketal as a single diastereomer. However, as shown in Scheme 10, the employment of alkynyl-4,5

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

• salts 1 with a broad scope of nucleophiles to produce diversely substituted valuable chromenoimidazopyridines under oxidative conditions (Scheme 1, reaction 2). Results and Discussion To prove the designed concept, the reaction between salicylaldehyde (2a), N-(cyanomethyl)pyridinium chloride (1) and

• nitromethane as a nucleophile was carried out in ethanol with triethylamine as a base under air atmosphere in a two-step fashion. Firstly, the quaternary salt was stirred with salicylaldehyde in the presence of triethylamine at 0 °C for 30 min, and secondly nitromethane (10 equiv) was added and the mixture was

• mixture was refluxed for 1 h. N-(Cyanomethyl)thieno[2,3-c]pyridinium chloride (15) and 6-(cyanomethyl)-1-methyl-1H-pyrrolo[2,3-c]pyridin-6-ium chloride (16) in reactions with salicylaldehyde and different nucleophiles. aSecond step was performed at 0 °C, for 7 days; b10 equiv of CH3NO2 was used. The

Copolymerization of epoxides with cyclic anhydrides catalyzed by dinuclear cobalt complexes

• Yo Hiranoi and
• Koji Nakano

Beilstein J. Org. Chem. 2018, 14, 2779–2788, doi:10.3762/bjoc.14.255

• (Scheme 1) [40]. First, the reaction of bis(salicylaldehyde) 5 with (R,R)-half-salen 6, which was prepared from (R,R)-1,2-cyclohexanediamine monohydrochloride and 3-tert-butyl-5-fluoro-2-hydroxybenzaldehyde, gave monosalen (R,R)-7 in 39% yield. Then, the obtained mono(salen) (R,R)-7 was converted into the

• heterochiral bis(salen) ligand precursor (R,R,S,S)-8 in 52% yield through the condensation with (S,S)-half-salen 6. In addition, the homochiral bis(salen) ligand precursor (R,R,R,R)-8 was prepared by the reaction of bis(salicylaldehyde) 5 with two equivalents of (R,R)-half-salen 6 in 45% yield. Both, (R,R,S,S

• tube containing bis(salicylaldehyde) 5 (0.72 g, 1.4 mmol), Et3N (0.47 mL, 3.4 mmol) and dichloromethane (7 mL). The reaction mixture was stirred at room temperature for 18 h and the resulting suspension was filtered off with dichloromethane. The filtrate was concentrated under reduced pressure and the

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

• substituents on the chromene core and 1,2,3-triazole offer a lot of possibilities for further derivatization and optimization towards biologically relevant structures such as flavonoid structures. Our group developed a Knoevenagel-assisted three-component reaction of (protected) salicylaldehyde, ethyl

• reaction was further optimized using salicylaldehyde (1a), β-nitrostyrene (2a) and benzyl azide (3a) as model substrates (see Supporting Information File 1, pages S4–S8 for full description of the optimization study). The optimized conditions for the one-pot three-component reaction were determined to be 1

• equivalent nitroalkene, 1.2 equivalents of salicylaldehyde and 0.1 equivalents of DABCO as catalyst in the first step at 40 °C, and 2 equivalents of benzyl azide, 2 equivalents of acetic acid, 0.3 equivalents of BHT as antioxidant, 4 Å MS and DMF under argon atmosphere at 120 °C in the second step. Crude NMR

Synthesis of 3-aminocoumarin-N-benzylpyridinium conjugates with nanomolar inhibitory activity against acetylcholinesterase

• Nisachon Khunnawutmanotham,
• Cherdchai Laongthipparos,
• Patchreenart Saparpakorn,
• Nitirat Chimnoi and
• Supanna Techasakul

Beilstein J. Org. Chem. 2018, 14, 2545–2552, doi:10.3762/bjoc.14.231

• compounds 4a, 5a, 9a–9i, and 10a were synthesized as shown in Scheme 1. 3-Acetamidocoumarin (2) was prepared following Dakin’s procedure [16] by reacting salicylaldehyde (1) with N-acetylglycine in acetic anhydride at 110 °C for 7 h. Hydrolysis of 2 with 50% HCl in ethanol at 100 °C for 1 h provided 3

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• of cytotoxicity, structure–activity relationships and electrochemical behaviour [95]. Derivatives that contain an aromatic amine and salicylaldehyde or 2-pyridinecarboxaldehyde moieties were found to be the most active against the HL-60 (promyelocytic leukaemia) cell line. Zhou et al. obtained

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• . Reactions with oxygen nucleophiles: In 1964 Schweizer reported the synthesis of 2H-chromene (39) by reaction of vinyltriphenylphosphonium bromide (8) with salicylaldehyde sodium salt in a yield of 62–71%, depending on the reaction conditions (Scheme 27) [1]. In a similar reaction with the use of 3-hydroxy-2

Mechanically induced oxidation of alcohols to aldehydes and ketones in ambient air: Revisiting TEMPO-assisted oxidations

• Andrea Porcheddu,
• Evelina Colacino,
• Giancarlo Cravotto,
• Francesco Delogu and
• Lidia De Luca

Beilstein J. Org. Chem. 2017, 13, 2049–2055, doi:10.3762/bjoc.13.202

• alcohol under mechanical activation conditions provided the salicylaldehyde in nearly quantitative yield (compound 2k in Scheme 3). The reaction was also successfully expanded to heteroaromatic alcohol 1l (Scheme 3, 2-furylmethanol), giving furfural in a very good yield (90%). The mechanically induced

Synthesis and metal binding properties of N-alkylcarboxyspiropyrans

• Alexis Perry and
• Christina J. Kousseff

Beilstein J. Org. Chem. 2017, 13, 1542–1550, doi:10.3762/bjoc.13.154

• synthesis of N-alkylcarboxyspiropyrans (e.g., C4SP) involves N-alkylation of 2,3,3-trimethylindolenine (1) with a bromoalkanoic acid or ester 2, isolation of the resulting indolium salt 3 or treatment with base to generate the exo-methylene enamine 4, then condensation with the appropriate salicylaldehyde 5

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

• invented an unprecedented effect of salicylaldehyde, one of the A3 coupling partners, which could lead to the formation of propargylamine, an important pharmaceutical building block, in the absence of any metal catalyst and under mild conditions. The role of the hydroxy group in ortho position of

• salicylaldehyde has been explored, which presumably activates the Csp–H bond of the terminal alkyne leading to the formation of propargylamines in good to excellent yields, thus negating the function of the metal catalyst. This observation is hitherto unknown, tested for a variety of salicylaldehyde, amine and

• acetylene, established as a general protocol, and is believed to be of interest for synthetic chemists from green chemistry. Keywords: A3 coupling; metal-catalyst-free; propargylamine; salicylaldehyde; terminal alkyne; Introduction Propargylamines are important synthetic intermediates for the preparation