Transition metal-catalyzed [2,3]-sigmatropic rearrangements of ylides: An update of the most recent advances

Photochemical ring expansion reactions: synthesis of tetrahydrofuran derivatives and mechanism studies

“…Ylides are important reaction intermediates in sigmatropic rearrangement reactions and serve as highly versatile synthons for the construction of complex molecular scaffolds. 1 Despite signicant advances over the past decades, 2,3 the basic understanding of the rearrangement process of oxygen or sulfur ylides is still limited and currently available synthesis methods underpin a substantial difference of the reaction mechanism of sulfur vs. oxygen ylides. 3,4 Both are typically accessed from unsymmetrically substituted (thio)ethers in the presence of a metal catalyst.…”

Substrate‐Controlled Cyclopropanation Reactions of Glycals with Aryl Diazoacetates

“…[3][4][5] Despite these advances current synthesis methods employing carbene transfer reactions are limited to the use of ethyl diazoacetate [3b,c] (Scheme 1a), intramolecular processes [4] and cyclic diazoamides. [5] The reaction with donor-acceptor substituted diazoalkanes [6] has, to the best of our knowledge, not been reported yet, although it would constitute an important strategy to introduce molecular complexity and to access cyclopropanated saccharides (Scheme 1b).…”

Metal-Bound or Free Ylides as Reaction Intermediates in Metal-Catalyzed [2,3]-Sigmatropic Rearrangements? It Depends.

“…Chemists have made strides in stereoselective, ylide rearrangements with electrophilic metal carbenes: not only are these reactions highly stereoselective, but they often show excellent chemo-and regioselectivities. 8,[12][13][14][15][16][17][18][19][20] The focus on metal carbenes 21 for this reaction, and in particular, rhodium (Rh) carbenes generated in situ from diazo compounds and metal catalyst, [22][23][24][25][26] has in large part been motivated by the ability to control stereoselectivity by exploiting different chiral ligands. Rh carbenes 24 are now commonplace in organic synthesis and especially useful in C-H activation chemistry.…”