Preparation of a Key Tetraene Precursor for the Synthesis of Long Acenes

Abstract

The tetraene 7,7‐dimethoxy‐2,3,5,6‐tetramethylenebicyclo[2.2.1]heptane is a key compound for the preparation of a large variety of acenes protected by a carbonyl bridge. We report herein a medium scale preparation in seven steps of this valuable starting material. Diels–Alder addition between 6,6‐dimethtyl fulvene and maleic anhydride, followed by carboxylation, ozonolysis of the double bond, reduction of the four ester groups, then chlorination of the alcohol groups and dehydrochlorination give the target compound in 17 % overall yield.

A Large Starphene Comprising Pentacene Branches

“…To elucidate the electronic properties of 1, we measured its absorption spectrum in a frozen matrice and compared it with that of pentacene [20,26] (Figure 3c) prepared under similar conditions from a carbonylated pentacene precursor (see Figure S29 for its structure). Solutions of 8a, 8b, respectively, were prepared in toluene with concentrations 10-4 mol.l-1 and the spectra recorded at room temperature (Figure S27a, S28a).…”

Synthesis and Absorption Properties of Long Acenoacenes

“…The synthesis of key dienes starts from the tetraene compound 4 which was prepared by our optimized synthetic protocol. [24] The diene 7, used for construction prototypal pentacenopentacene 1 was prepared in two synthetic steps (Scheme 1) starting by reaction of tetraene 4 with an in situ formed benzyne intermediate generated from commercially available 2-(trimethylsilyl)phenyl-trifluoromethanesulfonate 5. The not fully aromatized diene 6, formed in 64 % yield, was oxidized by DDQ providing diene 7 in 95 %.…”

A Large Starphene Comprising Pentacene Branches

“…We have synthesised [16]starphene 1 in 7s teps,s tarting from the 7,7-dimethoxy-2,3,5,6-tetramethylenebicyclo[2.2.1]heptane 2 [20,21] (Scheme 1). First, aDiels-Alder (DA) reaction of benzyne,generated in situ from commercially available 2-(trimethylsilyl)phenyl-trifluoromethanesulfonate,w ith one diene side of 2,g ave 3 in 64 %y ield.…”

“…To elucidate the electronic properties of 1,w em easured its absorption spectrum in af rozen matrice and compared it with that of pentacene [20,26] (Figure 3c)p repared under similar conditions from ac arbonylated pentacene precursor (see Figure S29 for its structure). Solutions of 8a, 8b, respectively,w ere prepared in toluene with concentrations 10 À4 mol L À1 and the spectra recorded at room temperature ( Figure S27a, S28a).…”