Syntheses of Donor–Acceptor-Substituted 2,6-Stellanes

Abstract

A number of condensations could be carried out using tricyclo[3.3.0.03,7]octane‐2‐one (stellanone, 4) and tricyclo[3.3.0.03,7]octane‐2,6‐dione (2,6‐stelladione, 5) as starting materials. The components for condensations were 2‐trimethylsilyl‐1,3‐dithiane (6), 1,1‐bis(trimethylsilyl)‐1H‐cyclopropa[b]naphthalene (7), its 3,6‐dimethoxy‐substituted analogue 8, fluorene (12), xanthene (13), diethyl malonate (14), and malononitrile (15). The condensation reactions with 5 yielded mono‐ and disubstituted products, among them were the donor–acceptor‐substituted 2,6‐stellanes 33–35. The structures of 18 (prepared from stellanone and fluorene), 19, 24, 27, 31 and 32 (synthesized by condensation of 2,6‐stelladione and 2‐trimethylsilyl‐1,3‐dithiane and malononitrile, respectively) were determined by X‐ray crystallography.

Syntheses and Properties of Donor−Acceptor-Substituted Molecules with a Bicyclo[2.2.1]heptane, a Bicyclo[2.2.2]octane, and a Tricyclo[3.3.0.03,7]octane Spacer

“…As the donor systems we used fluorene and xanthene, and as acceptor groups ester and cyano substituents. [14] The reaction products of stellanone and stellanedione with fluorene and xanthene (4Ϫ7) showed no or only a very weak fluorescence. This observation was supported by investigations of the condensation products between cyclohexanone and fluorene and xanthene, respectively.…”

“…This observation was supported by investigations of the condensation products between cyclohexanone and fluorene and xanthene, respectively. [15] As a next generation of donor substituents we introduced the cyclopropa[b]naphthalene moiety [14] which was expected to have good fluorescence properties. A series of investigations on 8, 9, and related systems showed good fluorescence properties on the one hand but photolability on the other.…”

“…The yields of the tricyclic systems 31, 33, 35 varied between 30 and 40% while for the bicyclic derivatives 30, 32, and 34 the yields were above 70%. To obtain the 2,5-donorϪacceptor-substituted stellanes 38Ϫ40 (Scheme 4), we first synthesized 37 [14] in a Knoevenagel condensation with the diketone 36 and propanedinitrile (21) in the presence of ammonium acetate/acetic acid. This affords 37 in 75% yield.…”

“…This affords 37 in 75% yield. [14] Scheme 4. Synthesis of 37؊40; a: NH4OAc, HOAc/toluene; b: LDA/THF The reaction of 37 with the phosphonates 12Ϫ14 provides the 2,5-donorϪacceptor-substituted stellane derivatives 38Ϫ40 in moderate yields.…”

“…This result supports the observation that stellanone reacts with propanedinitrile to give the corresponding (tricyclo[3.3.0.0 3,7 ]octan-2-ylidene)propanedinitrile in only 2% yield. [14] For comparison we also synthesized (bicyclo[2. …”