(3+3)‐Annulation of Carbonyl Ylides with Donor–Acceptor Cyclopropanes: Synergistic Dirhodium(II) and Lewis Acid Catalysis

Abstract

The first (3+ +3)-annulation process of donoracceptor cyclopropanes using synergistic catalysis is reported. The Rh 2 (OAc) 4 -catalyzed decomposition of diazoc arbonyl compounds generated carbonyl ylides in situ. These 1,3dipoles were converted with donor-acceptor cyclopropanes, activated by Lewis acid catalysis,toaffordmultiply substituted pyran scaffolds in high yield and diastereoselectivity.Extensive optimization studies enabled access to 9-oxabicyclo-[3.3.1]nonan-2-one and 10-oxabicyclo[4.3.1]decen-2-ol cores, exploiting solvent effects on intermediate reactivity.

Spirocyclic Amide Acetal Synthesis by [CpRu]‐Catalyzed Condensations of α‐Diazo‐β‐Ketoesters with γ‐Lactams

“…Decomposition of diazo derivatives in the presence of Lewis bases is a recognized strategy to generate ylides efficiently [1–9] . With aldehydes and ketones, but also esters and amides, carbonyl ylides are formed, usually under light irradiation or metal‐catalyzed conditions ( Scheme 1, A ) [8,10–25] . These reactive intermediates condense to form epoxides ( A , path a ), act as 1,3‐dipoles in intra‐ and intermolecular cycloadditions ( A , path b ) or form enol ethers ( A , path c ) [26–30] .…”

Synthesis of Diverse Heterocyclic Scaffolds by (3+3) and (3+4) Cycloannulations of Donor‐Acceptor Vinylcyclopropanes

“…[3] Although a wide range of five-membered heterocycles can be accessed in this way starting from imines, [4] aldehydes (or ketones), [5] nitriles, [6] and nitrones (or nitronates), [7] further increase of structural complexity is still underdeveloped, with the notable exception of indoles. [8] Moreover, the lack of 1,3-and 1,4-dipolar reaction partners (which are far less abundant compared to 1,2-dipolarophiles), has hindered the similar development of (3 + 3) [9] and (3 + 4) [10] cycloannulations, limiting the applications of these transformations. In an effort to overcome this restriction, our group recently reported the use of vinylcyclopropanes bearing a phosphonate group as an acceptor moiety in a palladium-catalyzed cycloannulation with salicylaldehydes to give benzoxepins.…”

Regio‐ and Diastereoselective Dimerization of Diazo Carbonyls: A Cooperative Catalytic Approach to Complex Scaffolds with Four Contiguous Stereocenters

“…[12] In 2019, our group developed the transformation with ad onor-acceptor cyclopropane, andv ery recently the Schneider group employed such an in situ generated 1,3dipole in a( 4 + +3)-cycloaddition reactionw ith ortho-quinone methides. [13] Latest studies have mainly focused on reactions of these in situ generated fleeting intermediates with dipolarophiles. When no other reactionp artners in the reaction of 1 are present and Rh II is the sole active catalyst, the well-known C 2 -symmetric dimerization products 2 are formed (Scheme 1B).…”