Assembling Complex Structures through Cascade and Cycloaddition Processes via Non-Acceptor Gold or Rhodium Carbenes

Abstract

AbstractThe ability of highly energetic metal–carbene intermediates to engage in complex cascade or formal cycloaddition processes is one of the most powerful tools for building intricate molecular architectures in a straightforward manner. Among this type of organometallic intermediates, non-acceptor metal carbenes are particularly challenging to access and, therefore, have experienced slower development. In this regard, our group has exploited the use of electrophilic gold(I) complexes to selectively activate certain classes of substrates for the generation of this type of intermediate. Thus, very different types of molecules, such as enynes or 7-substituted cycloheptatrienes, lead to the formation of carbenes under gold(I) catalysis. Related rhodium(II) carbenes can also be generated from cycloheptatrienes. In this account, we aim to summarize our efforts towards the in situ generation of such highly versatile organometallic species as well as studies on their reactivity through formal cycloadditions or complex cascade reactions.1 Introduction2 Generation of Au(I)-Vinylcarbenes via a Cycloisomerization/1,5-Alkoxy Migration Cascade2.1 Intramolecular Trapping of Au(I) Vinylcarbenes2.1.1 Applications in Total Synthesis2.2 Intermolecular Trapping of Au(I) Vinylcarbenes2.2.1 Total Synthesis of Schisanwilsonene A2.2.2 Trapping with Furans, 1,3-Dicarbonyl Compounds and Cyclic Alkenes2.2.3 Mechanism of the Cycloisomerization/1,5-Migration Sequence and the Role of the OR Migrating Group2.2.4 (4+3) Cycloadditions from Enynes3 Formal Cycloadditions of Simple Donor Metal Carbenes3.1 The Metal-Catalyzed Retro-Buchner Reaction3.2 Formal Cycloadditions with Non-Acceptor Carbenes via Metal-Catalyzed Aromative Decarbenations3.2.1 (4+1) Cycloadditions of Au(I) Carbenes3.2.2 (3+2) Cycloadditions of Au(I) Carbenes3.2.3 (4+3) Cycloadditions of Rh(II) Carbenes4 Concluding Remarks