1,4-BENZADIYNE EQUIVALENT

The procedure given here is a modification of the first synthesis of the tetrahydroanthracene diepoxides.5 7 These compounds have also been prepared from another 1,4-benzadiyne equivalent, namely 1,5-diamino-1,5-dihydrobenzo[1,2-d 4,5-d ]bistriazole which, although it has certain advantages,12 is not as available as 1,2,4,5-tetrabromobenzene. 

Khalil Shahlai, Samuel Osafo Acquaah, and Harold Hart 201 USE OF 1,2,4,5-TETRABROMO-BENZENE AS A 1,4-BENZADIYNE EQUIVALENT anti- AND syn-1,4,5,8-TETRAHYDROANTHRACENE 1,4 5,8-DIEPOXIDES... 

Bistriazole (508) served as a formal 1,4-benzadiyne equivalent in a sequence of two Diels-Alder additions to 2-methoxycarbonylfuran (509), which yielded (511) as the sole regio- and (tentatively assigned) stereo-isomer (Scheme 119). It appears, therefore, that the C02Me group, in the transient monoadduct (510), controls the orientation in the second step. 

Cycloaddition of benzyne (478) to (the less aromatic) anthracene provides a well-known approach to triptycene (524). More recently, this type of reaction was extended to elegant syntheses of iptycenes, e.g. (526), using 1,2,4,5-tetrabromobenzene (525) as a 1,4-benzadiyne equivalent (Scheme 123). ... 

Anthracenes react to give iptycenes 448 all of these reactions, the 1,2,4,5-tetrahalobenzene acts as the synthetic equivalent of 1,4-benzadiyne 434. 

By using a 1,2,3,4-tetrahalobenzene in which metal-halogen exchange occurs preferentially at the 1 and 4 halogens, one has a synthetic equivalent of 1,3-benzadiyne 433 . For example, the highly strained permethylphenanthrene 454 can be synthesized in this way by a double cycloaddition to 452. Initial exchange occurs primarily at the iodine atoms of 452. 

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