ChemInform Abstract: Ungewöhnliche Reaktivität gespannter Brückenkopfderivate.

Abstract

Unusual Reactivity of Strained Bridgehead DerivativesThe solvolysis of 7,7-dimethyl-1 ,exo-2-bis(trifluoromethylsulfonyloxy)norbornane (5) in Et20/ I,Mg and 80% MeOH proceeds with formation of substituted 2-norbornyl cations, yielding 1 ,exo-2-diiodo-7,7-dimethylnorbornane (9) and camphenilone (13), respectively. When the oic-diiodide 9 is treated with LiAIH,/C6H6 partial epimerization to 1 ,endo-2-diiodo-7,7-dimethylnorbornane (12) is observedwithout reduction; this result is probably due to steric hindrance of the reactants. Im folgenden berichten wir iiber die ungewohnliche hohe Reaktivitat des Briickenkopfderivates 7,7-Dimethyl-l ,exo-2-bis(trifluormethylsulfonyloxy)norbornan (5). Ergebnisse und DiskussionDas oic-Bistriflat 5 wurde durch Umsetzung von Camphenilon (13) mit Trifluormethansulfonsaureanhydrid (Tf20) hergestellt (Ausb. 60V0)~). Die Solvolyse von 5 in einer LOsung von Magnesiumiodid in absol. Ether ergibt 79% 1 ,exo-2-Diiod-7,7-dimethylnorbornan (9). Diese Umsetzung ist somit ein einfaches Verfahren zur Darstellung oic-Diiodide, einer neuen vor kurzem noch unbekannten, theoretisch interessanten Verbindungsklasses).Die milden Reaktionsbedingungen unter denen die Solvolyse von 5 verlauft schlienen die Bildung von Briickenkopf-Kationen als Zwischenstufen aus, wobei wir den folgenden Mechanismus fur wahrscheinlich halten. Dabei haben wir die klassische Schreibweise der 2-Norbornyl-Kationen 0 Verlag

Trifluoromethanesulfonate Anion as Nucleophile in Organic Chemistry

“…22 The reaction of β-pericyclocamphanone with a triflic anhydride/triflic acid mixture results in the formation of a rearranged ditriflate (Scheme 5), 23 through a process initiated by nucleophilic ring opening of the cyclopropane by triflate, and completed by trapping of a tertiary cation by triflate following a series of 1,2-shifts and dehydrations. Triflate also serves as the nucleophile in the capture of carbenium ions generated by rearrangements of polycyclic aldehydes in the presence of benzoyloxy triflate.…”

“…Other early indications of the nucleophilicity of triflate toward reactive cation-like electrophiles include the reaction of a spiro[5.2]­octanone with triflic anhydride leading to the formation of two vinyl triflates, one of which involved nucleophilic cleavage of the spirocyclic system (Scheme ). The reaction of β-pericyclocamphanone with a triflic anhydride/triflic acid mixture results in the formation of a rearranged ditriflate (Scheme ), through a process initiated by nucleophilic ring opening of the cyclopropane by triflate and completed by trapping of a tertiary cation by triflate following a series of 1,2-shifts and dehydrations. Triflate also serves as the nucleophile in the capture of carbenium ions generated by rearrangements of polycyclic aldehydes in the presence of benzoyloxy triflate .…”