Aliphatic Chemistry of Fluorene: Part Viii. Benzyl 9-Fluorenyl Sulphoxide and Some 9-Fluorenyl Sulphides

Abstract

Allyl 9-fluorenyl sulphide, benzyl 0-fluorenyl sulphide, and di-0-fluorenyl s~~l p h i d e are stable to boiling ethereal phenyl lithiun~, in marlied contrast to the corresponding ethers. Benzyl 9-fluorenyl sulphoside has been prepared and shown to be more weakly acidic than 9-fluorenyl sulphones.Wittig and co-worlcers have reported ( I ) that the anions (I) derived from certain 9-fluorenyl ethers rearrange to the corresponding 9-substituted-9-fluorenyl allioxides (11). Of particular interest to the present study were the ailions of the allyl and benzyl ethers (I, R = CHZCH=CH2 and CGHbCH?, respectively) which rearranged very rapidly a t -10". The anion of di-9-fluorenyl ether rearranged a t room temperature but those of other allryl and aryl ethers required elevated temperatures and longer reactioil times.These reactions belong to a wider group lcnown as the Stevens rearrangement (2, pp. 527-528; 3, pp. 282-283; 4). Most of the published work has been concerned with ethers (1,5, 6,7,8) but Hauser and co-worlcers have examined some sulphides (4). Both benzyl methyl sulphide and dibenzyl sulphide underweilt the Stevens rearrangement, more typical of the reactions of quaternary a~ninoniun~ compounds. Similar rearrangeinents have been reported for some sulphonium co~npounds (4,9). Although allylamine-Noxides show allylic rearrangement: from nitrogen to oxygen (10, l l ) , related allyl (12) and benzyl (4) sulphoxides and sulphones do not rearrange. Allyl phenyl sulphide and allyl p-tolyl sulphide possibly undergo the ortho Claiseil rearrangement (13; cf. ref. 14) b u t more slowly than the correspo~lding ethers. Ulllilie the ether, t-butyl phenyl sulpllide does not rearrange when distilled (15, IG).We have now prepared by a general method (17) allyl 9-fluorenyl sulphide, beilzyl 9-fluorenyl sulphide, and di-9-fluorenyl sulpl~ide. All three sulphides dissolved in ethereal solutioils of phenyl lithiuin with formation of the deep red color associated with fluorene anions of this type (1, 18) but the color was apparently unchanged after boiling under reflux for up t o 24 hours. Hydrolysis with water regenerated the original sulphides. Thus the anions of the sulphides are more stable than those of the ethers, resembling the 9-fluorenyl-triallrylai~linoi~ium compounds in not undergoiilg the ortho rearrangement (19).

Fulvenes and substituted fulvenes

“…In some of these cases, undoubtedly the anion CCLXIII is responsible for the dehydrogenation step. A similar reaction is the formation of VI in 9% yield in the pyrolysis of di(9fluorenyl) sulfide (26); simple pyrolysis of bis(biphenylene) ethane may well cause disproportionation and thus lead to VI and fluorene (189).…”