Formation of Active Cyclic Five-membered Frustrated Phosphane/Borane Lewis Pairs and their Cycloaddition Reactions |
| |
Authors: | Dr Shunxi Dong Dr Constantin G Daniliuc Dr Gerald Kehr Prof Dr Gerhard Erker |
| |
Institution: | Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany |
| |
Abstract: | The cyclic five-membered frustrated phosphane/borane Lewis pairs 11 a , b featuring the bulky octaethylhydrindacenyl- (Eind) substituent or its mono-bromo derivative (BrEind) at phosphorus are monomeric at room temperature. The reactive frustrated Lewis pairs (FLPs) cleave dihydrogen. The cyclic FLP 11 b (BrEind) undergoes 1,2-P/B addition to ethylene to give the zwitterionic heteronorbornane derivative 14 b . It reacts similarly with the carbon–carbon double bond of norbornene. With a variety of organic π-reagents, the cyclic FLP 11 b often undergoes reaction sequences reminiscent of the Alder–Rickert reaction: the cycloaddition reaction is followed by rapid cycloreversion to form new five-membered heterocyclic FLP products with extrusion of ethene. Reactions of 11 b with benzaldehyde or with acetylenes follow this reaction pattern. |
| |
Keywords: | boron cycloaddition cyclo-FLPs frustrated Lewis pairs phosphorus |
|
|