Platinum‐Catalyzed Intramolecular [4C+3C] Cycloaddition between Dienes and Allenes

Abstract

Crossing the seven C's: The three carbon atoms of several allenyl fragments can be incorporated into seven‐membered carbocycles by means of a Pt‐catalyzed intramolecular [4C+3C] cycloaddition with dienes (see scheme). The transformation provides a straightforward and atom‐economical entry to a variety of cycloheptane‐containing polycycles from readily available acyclic precursors.

Concerted and Stepwise Mechanisms in Metal‐Free and Metal‐Assisted [4+3] Cycloadditions Involving Allyl Cations

“…2 kcal mol À1 ; Table 1, entries 2 and 8-10), which suggests that the metal (Au, Pt, or Pd) has little effect in the cycloaddition reaction. Thus, it is not surprising that similar values of activation and reaction energies were found in the series of Au I complexes bearing different s donor ligands, such as phosphines (Table 1, entries [3][4][5] or N-heterocyclic carbene (entry 7).…”

“…To avoid these shortcomings, some of us recently reported a novel metal (Pt and Au)-catalyzed [4C + 3C] cycloaddition between dienes and tethered allenes, which provides a short and stereoselective route to synthetically useful bicycloA C H T U N G T R E N N U N G [5.3.0]decane skeletons like 5. [4,5] Most probably, the reaction involves a concerted [4 + 3] cycloaddition from the initially formed complex 3 to produce the metalcarbene complex 4 and subsequent 1,2-H-shift with simultaneous coordination of the newly formed C=C double bond to the metal (Scheme 1). [5] Similar to other pericyclic reactions, such as [4 + 2] DielsAlder or [3 + 2] cycloadditions, it is very likely that both metal-free and metal-catalyzed [4 + 3] transformations occur through highly concerted and aromatic transition states.…”

Gold catalysis-facilitated rapid synthesis of the daphnane/tigliane tricyclic core

“…[13] The gold-catalyzed furan/allene [4+3] cycloaddition, developed by the groups of Mascareñas [14] and Toste [15] , is a very efficient synthetic method for highly functionalized 7-membered ring construction. Despite the high efficiency in constructing polycyclic ring systems, its application in complex natural product synthesis has been very rare.…”

Total Syntheses of the Reported Structures of Curcusones I and J through Tandem Gold Catalysis

“…[11] For the synthesis of the rhamnofolane diterpenes, we envisioned a different tandem gold-catalyzed furan formation [12] and furan-allene [4+3] cycloaddition [13] to construct the 5,7-fused ring system with an oxa-bridge (Scheme 1B, 12 → 15 ). The tandem process is expected to proceed through a gold-catalyzed 5- endo - dig cyclization of enyne alcohol 12 and the resulting dihydrofuran would then isomerize to furan 13 .…”

“…During the cycloaddition, the allene would be converted to an allylic cation, therefore the allene axial chirality may be inconsequential. [13b] We envisioned a Diels-Alder reaction of diene 16 and methyl acrylate to build the 6-membered ring and the Diels-Alder product 17 would then be advanced to curcusone I ( 7 ) and J ( 8 ).…”