Furans Act as Dienophiles in Facile Diels−Alder Reactions with Masked o-Benzoquinones

Cr(CO)3‐Activated Diels–Alder Reaction on Single‐Wall Carbon Nanotubes: A DFT Investigation

“…[13] The use of polycyclic aromatic hydrocarbons as dienophiles has been scarcely documented; [22,23] there have also been few examples of aromatic heterocyclic systems employed as dienophiles in DA reactions. [24][25][26] Motivated by the recent experimental findings by MØnard-Moyon et al [13] and by the relevance of the cycloaddition reactions in the functionalization of CNs, [10] we decided to explore the DA reaction of 1,3-butadiene on the sidewalls of extended (5,5) CN models by means of high-level hybrid density functional theory (DFT) calculations. Our aim is to elucidate the DA reaction mechanism and the activation effect of Cr(CO) 3 on the reaction energetics.…”

Antitumor benzothiazoles. 13. (Diacetoxy)iodobenzene (DAIB) oxidation of 2-(4-hydroxy-3-methoxyphenyl)benzothiazole and related compounds in the presence of dienophiles

“…The yields are similar to those described in the literature using a thermally rather than a Lewis acid mediated Diels-Alder reaction. 15 The cycloaddition is relatively fast compared to that with electron deficient dienophiles, being complete in less than 15-20 minutes at 0 °C. Ethanol or propanol may replace methanol in the oxidation of vanillin generating mixed ketal intermediates.…”

“…The overall yields are relatively consistent at around 60%. The structures of the cis-decalins (15) were assigned largely on the basis of their NMR spectra. These structural assignments also compare well with those given for 15b in the literature.…”

Oxidative Conversion of Arenols into ortho ‐Quinols and ortho ‐Quinone Monoketals – A Useful Tactic in Organic Synthesis

“…In all cases, the cycloadditions are regiospecific and proceed with high diastereoselectivity, irrespective of the electronic demand and position of substituents on the 6,6-dimethoxycyclohexa-2,4-dienone core; only the chemical yields are affected [6]. Furans behave in a somewhat unusual manner as electron-rich dienophiles with these quinone monoketals [134,135]. Cintas and collaborators have also investigated the cycloaddition of furans with the ortho-quinone monoketal 76a [136].…”

“…Here again, the cycloaddition is endo-selective, with only regioisomers 79 being formed, and, when using 2-and/or 3-substituted furans, only the unsubstituted furan double-bond reacts in these inverse electron-demand Diels-Alder processes [134][135][136]. Indoles, pyrroles, and thiophenes can also be made to react as dienophiles with ortho-quinone monoketals 76a-c bearing an electron-withdrawing group at their 4-position [136,137].…”