CpRuCl(PPh₃)₂-Catalyzed Cyclopropanation of Bicyclic Alkenes with Tertiary Propargylic Acetates

Abstract

The electron-rich cyclopentadienylruthenium complex CpRuCl(PPh3)2 turns out to be an efficient catalyst for the regio- and stereoselective cyclopropanation of bicyclic alkenes with tertiary propargylic carboxylates. The reaction provides 1,2,3-trisubstituted cyclopropanes in high yields as a single stereoisomer instead of the expected cyclobutenes via [2 + 2] cycloaddition. Functional groups such as ethers, esters, alcohols, phenols, ketones, esters, carboxylic anhydrides, nitriles, halides, sulfones, imides, carbamates, and azines are tolerated with the catalyzed reaction. An efficient cyclopropanation of cyclobutenes was also demonstrated, providing the strained bicyclo[2.1.0(1,3)]pentane framework.

Recent Developments in the Metal‐Catalyzed Reactions of Metallocarbenoids from Propargylic Esters

“…Tenaglia and Marc have extended this reaction to alkenes that remained unreacted under the Uemuras conditions, [24] including strained norbornenes, norbornadienes, and benzonorbornadienes, with success, the Ru complexes [RuCp- 2 ] being the most efficient catalysts. [26] Pentannulation Reactions on Aromatic Ring Systems Pentannulation on aromatic or heterocyclic ring systems has emerged as a potent and useful tool in organic synthesis. [27] Very recently, propargylic esters have been investigated with success as suitable precursors in order to accomplish this task.…”

Interception of a Rautenstrauch Intermediate by Alkynes for [5+2] Cycloaddition: Rhodium‐Catalyzed Cycloisomerization of 3‐Acyloxy‐4‐ene‐1,9‐diynes to Bicyclo[5.3.0]decatrienes

“…[1,2] The scope of this rearrangement reaction has been expanded significantly by the use of π-acidic metals, [3] such as gold- and platinum-based catalysts, for the synthesis of functionalized five-membered rings. [4] The 1,2-acyloxy migration of propargyl esters has also been employed in other synthetically useful transformations catalyzed by gold, [5,6] platinum, [6,7] ruthenium, [8,9] copper, [6] and more recently rhodium. [10] …”

Use of ionic liquids in the platinum- and gold-catalyzed cycloisomerization of enyne systems

“…For instance, we [12][13][14][15][16][17] and others [18][19][20][21][22][23][24][25][26][27][28][29][30] have shown that different acyl groups at a propargylic position of an enyne can migrate in a 1,2-fashion with concomitant intramolecular cyclopropanation onto the ene part of the substrate. We demonstrated that acyclic propargylic enyne acetates such as 1 are useful precursors of bicyclic compounds 2 [12,15,31].…”