The Diels–Alder adduct of C₆₀ and 4,5‐dimethoxy‐o‐quinodimethane—synthesis, crystal structure, and donor–acceptor behavior

Abstract

is known to be a strong electron acceptor,"] and solid donor-acceptor complexes have been formed by co-crystallization of C,, and strong donors such as ferrocene.[21 Covalent linking of C,, and electron donors is expected to create attractive substrates for the study of electron or energy transfer. By making use of the cycloaddition route that we reported previously[31 we have now succeeded in synthesizing a 4,5-dimethoxy-o-quinodimethane-C,, adduct 3.[4-61 We describe the unique crystal structure and the determination of the bandgap of solid 3 by ESCA measurements.The mono-adduct 3 and the bis-adduct 4 have been prepared by the Diels-Alder reaction of C,, (1) with 6,7-dimethoxy-3-isochromanone (2) in boiling 1,2,4-trichlorobenzene for 24 h (Scheme 1). The chromatographic separaH3c0m0 HJCO 2 c,,= 1 I n 3 4 Scheme 1 . Reaction between C,, (1) and 4.5-dimethoxy-o-quinodimethane prepared in situ froin 6,7-dimethoxy-3-isochromaiione (2).

The X‐Ray Crystal Structures of a 1,9‐ and a 7,8‐Diels‐Alder monoadduct of C70

“…. O distance of 3.07 A has been found for 2, which co-crystallizes with benzene in the space group P 2 J n [Id] [5]. Fig.…”

“…Discussion of the Structures. -In a D5,,-(& fullerene, there are five independent types of atom, giving rise to eight different types of bond (four [86,6] and four [6,5] bonds, respectively) and 11 distinct bond angles. The designation of bond types and angles used in this paper is given in …”

“…Isomer lc, with a bridge at the C(22)-C(23) bond near the flatter equator, was produced in much lower yield than the two other isomers. A similar Diels-Alder adduct (2) of C,, had been previously prepared independently by two groups [Id] [5].…”

Diels–Alder cycloaddition as an efficient tool for linking π-donors onto fullerene C60

“…The [4 + 2] cycloaddition required o-quinodimethane precursors [27] generated in situ by various methods such as 1,4-reductive elimination from 1,2-bis (bromomethyl)benzene [24], thermolysis of 1,2-dihydroxycyclobutabenzene [28], thermal extrusion of sulfur dioxide from corresponding sultines [29] or sulfones [30], and extrusion of carbon dioxide from isochromanone derivatives [31] (Scheme 2).…”

Aromatic polyamides containing keto-benzocyclobutene pendants

“…Literature is replete with examples3 illustrating the versatile reactivity of oquinodimethane with a broad spectrum of dieno-philes ranging from a simple olefinic moiety4 to the esoteric buckministerfullerene ( C60). 5 While the substituents at the alicyclic ring of BCB moiety, i.e., carbons 1 and 2 (see Fig. l), are long known to be able to lower the ring-opening temperature (<200°C),6 only recently, substitution at the aromatic-ring positions ortho to the four-membered ring (i.e., carbon 3 and 6) has shown to have suppressing effect which was demonstrated to be of steric n a t~r e .~ Thus, 3,6-disubstituted benzocyclobutenes irrespective of the electronic nature of the substituents, are converted to o-quinodimethanes at temperatures about 100°C higher than typical for unsubstituted benzocyclobutenes.…”