The Total Synthesis of Naturally Occurring Oxygen Ring Compounds

Electron ionization‐induced fragmentation of some new dibenzo(d, f)(1,3)dioxepine derivatives

“…In particular, it has been found that the biphenyl scaffold is a privileged structure in pharmaceutical applications and is present in a wide range of active therapeutic compounds (antitumour, antiatherosclerotic and antihypertensive agents). 1,2 To our knowledge, only one communication has been published reporting the mass spectrometric behaviour of 6,6-dimethyl-dibenzo(d, f )(1,3)dioxepine, by Gross and coworkers. 3 In particular, they have reported a fragmentation process useful to determine the proximity of hydroxyl groups in polycyclic aromatic compounds.…”

“…2,2 0 -dihydroxybiphenyl (1), dibenzofurane (13) and 2-methoxybiphenyl (14), methoxyacetone, 4-methylacetophenone, 4-methyl-d 3 -acetophenone, d 6 -acetone as well as all the solvents were commercial products (Aldrich) and have been used without further purification. f) (1,3) dioxepine (4) A mixture of 2,2 0 -dihydroxybiphenyl (1) (5.37 mmol) and the respective ketone (21.48 mmol) was stirred under nitrogen for 20 min thin layer chromatography (TLC) at 60°C in the presence of indium(III) chloride (0.54 mmol). After the reaction, the crude mixture was separated by flash-column chromatography (hexane/dichloromethane 1/1) on silica gel, obtaining the desired products as yellow oil.…”

Development of Palladium-Catalyzed Transformations Using Propargylic Compounds

“…It is anticipated that the absolute configuration of the newly formed stereogenic center could be controlled by chiral palladium catalysts. 30,32,33) After several attempts, we found that the optically active cyclic carbonate (R)-37m was formed in 34% yield with 72% ee when the reaction of 36m with p-methoxyphenol was carried out in the presence of 5 mol% Pd 2 (dba) 3 (Table 12, entry 1). The yield was improved by carrying out the reaction under CO 2 atmosphere (75% yield with 71% ee, entry 2).…”

“…Proposed Reaction Mechanism for Production of 3 30) We next focused on the reactivity of 2-(2-hydroxyphenyl)acetates as the bis-nucleophile. By introducing phenolic oxygen and a carbon moiety as the nucleophilic part within the substrate, we thought that substituted chromans, common structures in many pharmaceutical and agricultural compounds, [31][32][33] could be synthesized in one step. The initial attempts were carried out using 1,3-diphenylprop-2-ynyl methyl carbonate (13a) and methyl 2-(2-hydroxyphenyl)acetate (14a).…”

Microwave Assisted Regioselective Synthesis and Biological Evaluation of Pyrano[2,3-c]Pyridine Derivatives Utilizing DMAP as a Catalyst

“…Pyrane and fused 4H-pyrane derivatives have concerned of interest (Dean, 1963) outstanding to their varied physiological activities. (Feuer, 1974) Earlier studies have presented that pyran derivatives possess pronounced chemical and biological activities, such antimicrobial activity, (Bonsignore et al, 1993;Ashraf, 2012) anti-coagulant, (Akbar et al, 2015;Dinesh et al, 2017) anti-tumor and anti-HIV.…”