Different Reactivity Patterns of Trimethylsilyl- and Phenyl-Substituted Propargylallenes: Fe₂(CO)₉- and [Ag]⁺-Promoted Cyclizations

Abstract

Thermolytic rearrangement of the diphenyl-propargylallene [3,3-(biphenyl-2,2 0 -diyl)-1-phenyl-1-{9-[(phenylethynyl]-9H-fluorenyl}allene], 9, yields the bis-fluorenyliden-bis-allene 10, which undergoes electrocyclization to form 3,4-di(fluorenyliden)-1,2-diphenylcyclobutene, 12, in which the overlapping fluorenylidenes give rise to C 2 symmetry. The propargylallene 9 reacts with iron carbonyls to form 15, in which an (η 5 -fluorenyl)Fe(CO) 2 moiety is linked both directly and via a bridging dC(Ph)-C(dO)linkage to a cyclobutene ring possessing a phenyl group and a spiro-bonded fluorenyl substituent. The diphenyl-propargylallene 9 and its bis(trimethylsilyl)propargylallene analogue, 2, each react with Co 2 (CO) 8 to furnish the corresponding alkyne-Co 2 (CO) 6 complexes 14 and 13, respectively. Treatment of the diphenyl-propargylallene 9 or the mono(trimethylsilyl)propargylallene 25 with silver nitrate in methanol or water effects cyclization of the allene onto the alkyne to furnish a cyclopentadiene that bears a 9-methoxy-or 9-hydroxy-fluorenyl substituent and is also spiro-bonded to a second fluorenyl moiety. The reaction of 3,3-(biphenyl-2,2 0 -diyl)-1-bromo-1-phenylallene with Fe 2 (CO) 9 yields the novel bicyclo-[3.2.0]heptadienone 21, which possesses two phenyl groups and is also spiro-linked to two fluorenyl fragments. All new compounds were characterized by NMR spectroscopy and X-ray crystallography.

C2-Symmetric 1,2-di(fluorenylidene)cyclobutanes: syntheses, structures, rearrangements and reactivity

“…The corresponding values in 20 were 2 J HH ¼14. 5 Hz and 3 J HH ¼6.2 and 1.0 Hz, indicating that in this case the dihedral angles between vicinal hydrogens are w35 and w90 . The tribromo derivative, 21, exhibits a 1 H NMR singlet at 6.13 ppm but, without X-ray data, one cannot unequivocally identify the isomer.…”

“…5 Hz doublets at 4.83 and 4.56 ppm. In addition, small quantities of the mono-bromo, 19 and 20, and tri-bromo, 21, derivatives were isolated chromatographically, and identified from their NMR spectra.…”

“…bromineA potential approach to the synthesis of 3,4-dibromo-1,2-di(fluorenylidene)-3,4-diphenylcyclobutane involves the addition of bromine to 3,4-di(fluorenylidene)-1,2-diphenylcyclo-butene, 24, readily available from the precursor propargylallene, 22, 20 via thermolysis and subsequent electrocyclization of diallene 23 (Scheme 7) 5. Upon dropwise addition of bromine to a cooled solution of 3,4-di(fluorenylidene)500 MHz 1 H NMR spectra showing the gradual evolution of a pure sample of 16 into an equilibrium mixture of 16 and 17 over a period of 2 weeks at room temperature.…”

Organic and Organometallic Derivatives of Propargylallene: Syntheses, Structures, Reactivity and Rearrangements

“…As part of a programme directed towards the syntheses of electroluminescent tetracenes, [21] 9-phenylethynyl-9Hfluoren-9-ol (21, Scheme 5, below) was converted into 3,3-(biphenyl-2,2Ј-diyl)-1-bromo-1-phenylallene (22) by treatment with hydrogen bromide in acetic acid; subsequent treatment with half an equivalent of butyllithium delivered the diphenylpropargylallene 23 as pale-yellow crystals (m.p. 284-286°C) in 43 % yield.…”

The chemistry of bisallenes

“…Derivative 150 can be desilylated to a C 60 H 36 hydrocarbon, whose C 36 backbone represents ca. 60% of the fullerene framework and which can be mapped onto C 60 [121]. …”