Arynes and Derived Compounds

Work on the reactions of tetrafluoro- and tetrachloro-benzyne with 6,6-dialkyl-fulvenes has now been reported in detail photoisomerization of the product from dimethylfulvene (132) gives the isopropylidenetetracycloundecatriene (133), and hydrogenation of the former compound has led to isolation of two dihydrocompounds (134) and (135) and the tetrahydro-derivative (136) [for the action of 

The complicated Russian work on the properties of polyfluorobenzocyclenes has continued apace with the publication of parts XI— XV and XVII— XXII 

Reagents i, HF ii, skeletal rearrangement iil, v. F attack from above at C-1 (gives main product) iv, F- attack from below at C-1. 

Derivatives of Nitrogen.— The preparation of amino-derivatives of perfluoromesityl-ene froth the parent compound and ammonia in ether has been claimed, and treatment of hexafluorobenzene with A -Iithium iV-ethylpentafluoroanilide gives the iV-ethy immoperfluoro-l,4-phenylenes (197 n = 1,2, and 3). 3,3 -Diamino-4,4, 6,6 -tetrafluoro-, 3,3 -diamino-2,2, 6,6 -tetrafluoro-, and 3,3 -diamino-2,2 -4,4, 6,6 -hexafluorobiphenyl have been synthesized by conventional nitration-reduction routes from the appropriate tetrafluoro- and hexafluoro-biphenyls, and treatment of the azo-compounds 098 X = Y = F, Z = H X = Z = F, Y = H X = OEt, Y =5 H, Z = F) with tin(ii) chloride and hydrochloric acid yields the conesponding benzidines (199).  

The phenacetin analogues (200 R = Me, Et, Pr , CHaCi, or CFa) have been synthesized from pentalluoronitrobenzene (Schrane 41), but preliiniiiary tests 

Reagents i, fttran-EtjO-cyclohexane ii, thiophen-CHjClj iii, I,-CHCla-BuOH  

Tetrachloro- and tetrafluoro-benzyne react with bicyclo [2,2,1 ]heptene (norbomene) to give exclusively the exo-adduct (139) (ca. 35% yields), and tetrabromo-, tetrachloro-, and tetrafluoro-benzyne react with bicyclo-[2,2,1 ]heptadiene (norbornadiene) to give (mainly) the [ 2 -i- 2] adduct (140) with some 2 -I- 2 -I- 2] adduct (141). The mechanisms of these reactions and the factors influencing the product ratios have been discussed.  

Thermal rearrangement of l,2,3,4-tetrafluoro-5,8-dihydro-5,8-(A -methyl-imino)naphthalene (142), the Diels-Alder adduct of tetrafluorobenzyne and A-methylpyrrole, in refluxing ethylene glycol or in benzene at 180 °C (sealed tube) affords A-methyl-2-(2,3,4,5-tetrafluorophenyl)pyrrole (143) in good 

7-I opropylidenetetrafluorobenzonorbomadiene (16S) (from diazotized tetrafluoroanthranilic acid and 6,6-dimethylfulvene) is attacked by halogen cations from the endS -side and yields, inter alia, the cu-di-eitdb-adduct (166) 

In contrast to the tetrafluorobenzonorbomadiene series, tetrafluorobenzo-barrelene (171) is attacked only from the ewfo-side by Br+ and I+, although C1+ is less selective halogenation is invariably accompanied by rearrangement of the hydrocarbon skeleton. However, the benzobarrelene reacts with perbenzoic acid to yield the ew-epoxide (172) and the endo,exo-diepoiad o (173). Treatment of the mono-epoxide with boron trifiuoride etherate yields 

---

Arynes and Derived Compounds.—The generation of tetiafluorobenzyne by thermal decomposition of the diazonium carboxylate (134), obtained by treatment of tetrafluoroanthranilic acid with n-butyl nitrite, was first reported some years ago, and Scheme 34 shows some recently described reactions of the benzyne generated in this way (see also p. 411 The reaction... 

---