Remarkable Efficiency of the Aryne Chemistry of (Dehydro)octafluoro[2.2]paracyclophane When Using the Cadogan Method

Abstract

Generation of the aryne, (dehydro)octafluoro[2.2]paracyclophane, from its acetamide derivative utilizing the Cadogan method led to remarkable results with respect to Diels-Alder and ene reactivity. A comparison was made between this new and virtually unused method and our earlier reported results using Cram methodology (reaction of aryl iodide with potassium tert-butoxide). Surprisingly, no ene reactivity was observed with the Cram methodology. This mechanistic conundrum was examined extensively with no unambiguous explanation for the difference in reactivity being found.

Sequential ene, Diels–Alder reactions of AF4-yne with 1,3,5-cycloheptatriene

“…This is the geometry found by a conformational search using MM2 in Hyperchem, and confirmed by the NOEs displayed by the products of the reaction of the AF4 arene with cyclopentene and with cyclohexene [2]. Two NOEs between 3.06 and 7.21 and between 5.50 and 7.11 allowed the assignment of the protons on the face of the other para-phenylene moiety of the AF4, as 7.21 being syn to 3.06.…”

“…This is the geometry found by a conformational search using MM2 in Hyperchem, and confirmed by the NOEs displayed by the products of the reaction of the AF4 arene with cyclopentene and with cyclohexene [2]. In compound 9, 1.97 displays NOEs with two aromatic protons at 7.08 and 7.40, while 1.67 does not, therefore, the other para-phenylene ring of the AF4 moiety bound to the cyclopropyl ring is on the same side of this ring as 1.97.…”

“…In a series of recent papers, we have demonstrated that the aryne generated by either the facile base-catalyzed elimination of HI from AF4-iodide or via Cadogan's method of thermal decomposition of the N-nitrosoacetamide derivative of AF4, has extraordinary Diels-Alder reactivity, providing yields of 84 and 91%, respectively, in their reactions with benzene (Scheme 1) [1,2]. In our most recent report, it was also shown that the aryne generated via the Cadogan procedure (but not by the Cram method) exhibited excellent ene reactivity, reacting with 1-octene to provide a 91% yield of its ene adduct (Scheme 2).…”

Discrimination of pseudo‐meta and pseudo‐para diamino‐octafluoro[2.2]paracyclophanes by 1H, 19F, and 13C NMR

“…The spectroscopy of these compounds is particularly interesting, and nuclear magnetic resonance (NMR) is no exception . With the advancements in syntheses of bridge‐fluorinated [2.2] paracyclophanes, and their potential utility as monomers in high‐performance polymers, the spectroscopy of this class of compounds has been an area of particular interest. The presence of fluorine atoms in this class of cyclophanes render these compounds amenable to study by 19 F NMR, which is highly sensitive and intrinsically information‐rich, and provides unique insight into their chemistry.…”

Novel ring-cleaving reaction of 4-nitro-1,1,2,2,9,9,10,10-octafluoro[2.2]paracyclophane with nucleophiles

“…Over the last decade, our broad studies of octafluoro [2.2]paracyclophane (AF4) and its derivatives have demonstrated that the highly electron-deficient aromatic rings of AF4 exhibit a rich diversity of chemical behavior, including clean, high yield electrophilic substitution and disubstitution [1,2] unique aryne reactivity [3] and excellent S RN 1-reactivity with soft nucleophiles such as phenyl thiolate and malonate anion (Scheme 1) [4]. In the present communication, we wish to report the unexpected discovery of an unusual ring-opening reaction of nitro-AF4 when it is treated with hard nucleophiles, such as alkoxides and cyanide ion.…”