An outstanding characteristic of the [2,]paracyclophanes is the through-space interaction of the two fully conjugated n-electron systems of the separate layers. As demonstrated by the electronic properties of these compounds, ['] the two layers afford one overall n-electron system.['I Very little is known, however, about this interaction in charged paracyclophanes. Diatropic anionic [2.2]paracyclophanes have previously been but no paratropic [2.2]paracyclophane systems have been reported.
We wish to report the first [2.2]paracyclophane in which a 4nn paratropic dianion interacts with a virtually neutral benzene moiety. In this case the benzene ring acts as an "observer," which is located in a well-defined position and can be used to probe the spatial interactions due to both charge and anisotropy effects.
The system of choice is 2.2benzo[g]chrysenoparacyclophane dianion 12', obtained by metal reduction of 2.2benzo[g]chrysenoparacyclophane 1 (Scheme 1). To synthesize this h y d r o c a r b ~n , ~~, ~] the phosphonate 2 (R = CH,PO(OEt),), prepared from 4-bromomethyl[2.2]paracyclophane 2 (R= CH2Br) by the Arbuzov reaction, was coupled with commercially available 9-formylphenanthrene in a Wittig-Horner reaction. The resulting trans olefin,[91 formed in 40% yield, was subsequently photocyclized by irradiation (Hanau TQ 150 lamp) in a toluene solution in the presence of iodine, providing the benzochrysenophane 1 19] (18%, colorless plates, m.p. = 267-269", dec.). By an analogous route, the chrysenophane 319] was prepared (34%, colorless needles, m.p.= 149-152ยฐC) with a Wittig reaction between 4-formyl[2.2]paracyclophane 2 2 d ) -q ) I d T / & L -, 3 -4 & ] : @ -3 20 -Scheme I. a) nBuLi, THF: b) 9-formylphenanthrene; c) hv, 12, toluene; d) NaH, THF; e) a-naphthyl-CHZPPh3Br; f) 2 (R=CHO), THF; g) Itv, 12, toluene.