General Synthetic Entry to Linearly-Fused Dihydrobenzocyclobutene-1,2-diones and Benzocyclobutene-1,2-diones via Annulation of 1,2-Bis(methylene)carbocycles with 3-Chloro-3-cyclobutene-1,2-dione¹

Abstract

The tandem Diels-Alder/dehydrochlorination reaction of semisquaric chloride (1) with the 1,2-bis(methylene)cycloalkanes 2a-c and 1,2-bis(methylene)-4-cyclohexene (9) affords the linearly-fused cycloalkanodihydrobenzocyclobutene-1,2-diones 3a-c and 3,4,7,8-tetrahydrocyclobuta[b]-naphthalene-1,2-dione (10), respectively. On treatment with MnO2, 3a-c are dehydrogenated to the respective carbocycle-fused benzocyclobutene-1,2-diones 4a-c in good yields. 3a and 3b react with bromine to give the addition products 5a,b, which, on treatment with silver trifluoroacetate, afford the benzocyclobutene-1,2-diones 4a,b. For preparative purposes, the sequence 3-->5-->4 can be performed advantageously as a "one-pot procedure". Double-condensation reactions of 4a,b with alpha,alpha'-biscyano-o-xylene and o-phenylenediamine afford the pentacyclic biphenylenes 7a,b and the cyclobutahetarenes 8a,b, respectively. These cyclobutenediones suggest themselves as building blocks for the construction of extended linearly-fused polycyclic compounds with novel ring sequences. o-Quinodimethanes 12a-g generated in situ by the thermal decomposition of the respective 1,4-dihydro-2,3-benzoxathiin-3-oxides (sultines) 11a-g react with semisquaric chloride (1) to afford the 3,8-dihydronaphtho[b]cyclobutene-1,2-diones 13a-g. These, on dehydrogenation with bromine and/or MnO2, furnish the naphtho[b]cyclobutene-1,2-diones 14a-g in fair to good yields. As described for 4a,b the naphtho[b]cyclobutene-1,2-diones 14a-c are condensed with alpha,alpha'-biscyano-o-xylene and o-phenylenediamine to furnish the pentacyclic biphenylenes 15a-c and the pentacyclic cyclobutahetarenes 16a-c.

Cyclobutarenes and Related Compounds

“…Using a similar approach, higher analogues of benzocyclobutenedione, i.e., cyclobuta[ c ]- and cyclobuta[ a ]phenanthrene-1,2-dione and cyclobuta[ a ]triphenylene-11,12-dione, can be prepared . Linearly fused dihydrobenzocyclobutenedine and benzocyclobutenediones are also prepared via annulation of 1,2-bis(methylene)carbocycles by 286 66 …”

Synthesis of Molecular Seesaw Balances and the Evaluation of Pyridinium−π Interactions

“…A new molecular balance 1 was prepared by the reaction of 1-azaanthracene , and o -quinodimethane generated from the corresponding sulfone or sultine in situ, as shown in Scheme . The cycloaddition reaction was first carried out using reaction conditions similar to those for the addition of anthracene and o -quinodimethane reported by Shishido, Noyori and Nozaki .…”

“…In addition, toluene can be used for the reaction at 280 °C, which allows much easier workup and purification compared to synthesis using diethylphtharate as a solvent . The cycloaddition with sultine 9 , which was often used as a precursor of o -quinodimethane, , also afforded the adduct 1 in 32% yield under similar reaction conditions. The use of dimethoxyphenyl sulfone 8 as a precursor of the corresponding o -quinodimethane provided adduct 5 with two methoxy substituents at the mobile unit in 13% yield.…”