Thermodynamically Stable o‐Quinodimethane: Synthesis, Structure, and Reactivity

Abstract

Thermal isomerization of cyclobutaphenanthrene to o‐quinodimethane was investigated. Sterically congested substituents or electron‐donating substituents on the four‐membered ring promoted the ring‐opening, affording o‐quinodimethane in a relatively stable form. Isolation of the newly prepared o‐quinodimethane allowed its structural elucidation and investigation of its potential reactivities. Dual [4+2] cycloaddition of an aryne and o‐quinodimethane afforded tetrabenzopentacene, demonstrating the synthetic application of the isolated compound.

Synthesis of Phenanthrene‐Based Polycycles by Gold(I)‐Catalyzed Cyclization of Biphenyl‐Embedded Trienynes

“…[13] Although reaction under the optimized conditions was found to be sluggish, increasing the temperature to 80 °C and the catalyst loading to 10 mol% resulted in the double gold-catalyzed cyclization, which was complete after 24 h (Scheme 6). Under these conditions, tetrabenzo-pentacene 11 [20] was selectively produced and could be isolated in a remarkable 43% yield.…”

Visible-Light-Mediated Catalyst-Free [2+2] Cycloaddition Reaction for Dihydrocyclobuta[b]naphthalene-3,8-diones Synthesis under Mild Conditions

“…The development of green, concise and mild synthetic methodologies for extensively used organic compounds is one of the most essential tasks in the area of organic synthesis. Fused cyclobutene is a type of unique and intriguing structural motif in organic chemistry, which has attracted considerable attention in recent years because it is luxuriant in nature and shows multiple biological activities [1][2][3][4][5][6][7][8][9]. Furthermore, owing to the high chemical reactivity from the inherent and high ring strain, the fused cyclobutenes experience diverse transformations, ring-opening and ring-expansion reactions in particular, providing distinctive approaches to the construction of complex organic molecules [10][11][12][13].…”

Recent Advances in Benzocyclobutene Chemistry

“…For instance, ivabradine (Figure 1) is a well‐known marketed drug to treat heart related problems, which contains BCB as a structural unit [2] . The unique structural feature of BCB makes it a key precursor in synthetic organic chemistry due to the formation of very reactive intermediates o ‐quinodimethanes ( o ‐xylylenes) through cyclobutane ring opening [2e,f] . This intermediate can be trapped easily and it undergo, inter‐ and intramolecular Diels‐Alder reaction with diverse dienophile or dimerization and polymerization [3] .…”