Abstract
Cyclopropane is one of the most reactive functionalities owing to its intrinsic ring
strain. Transition-metal catalysis and Lewis acid catalysis have been extensively
used in ring openings of cyclopropanes; however, Lewis base-catalyzed activation of
cyclopropanes remains largely unexplored. Upon nucleophilic attack with Lewis bases,
cyclopropanes undergo ring cleavage in a manner known as homoconjugate addition to
form zwitterionic intermediates, which have significant potential for reaction development
but have garnered little attention. Here, we present a brief overview of this area,
with an emphasis on our recent efforts on Lewis base-catalyzed rearrangement reactions
of electron-deficient cyclopropanes using the homoconjugate addition process.
1 Introduction
2 DABCO-Catalyzed Cloke–Wilson Rearrangement of Cyclopropyl Ketones
3 Hydroxylamine-Mediated Tandem Cloke–Wilson/Boulton–Katritzky Reaction of Cyclopropyl
Ketones
4 Phosphine-Catalyzed Rearrangement of Vinylcyclopropyl Ketones To Form Cycloheptenones
5 Phosphine-Catalyzed Rearrangement of Alkylidenecyclopropyl Ketones To Form Polysubstituted
Furans and Dienones
6 Conclusion and Outlook
Key words
Lewis base catalysis - cyclopropanes - homoconjugate addition - rearrangement - vinylcyclopropanes
- alkylidenecyclopropanes