Rhodium(II)‐Catalyzed Cross‐Coupling of Diazo Compounds

Abstract

Nothing left to chance: A convenient protocol for selective cross‐coupling of diazo compounds for the convergent synthesis of alkenes was developed (see scheme; EDG=aryl, heteroaryl, vinyl; R=O‐alkyl, aryl). The selectivity control elements were identified by ReactIR and DFT calculations and provide a framework for the design of viable diazo coupling reactions.

Using Soluble Polymers to Enforce Catalyst‐Phase‐Selective Solubility and as Antileaching Agents to Facilitate Homogeneous Catalysis

“…Both soluble supported catalysts we developed and insoluble supported catalysts others have used are recyclable in these processes 3. 4 However, all these catalysts require slow addition of the diazo substrate with a syringe pump because of the facile and exothermic Rh II ‐catalyzed dimerization of the diazo reactant 5. Here we describe how a soluble polymer’s phase‐selective solubility segregates the Rh II catalyst and diazo reactant in nonpolar and polar phases of a biphasic heptane/CH 3 CN mixture enabling both catalyst recycling and suppression of dimer formation without syringe pump addition of the N 2 CHCO 2 Et.…”

Gold(I)‐Catalyzed Diazo Coupling: Strategy towards Alkene Formation and Tandem Benzannulation

“…The gold-catalyzed cross-coupling is the preferred process, which is consistent with Davies previous investigation. [8] A plausible mechanism for the gold(I)-mediated crosscoupling of vinyldiazoacetates is proposed (Scheme 4). First, the preferential reaction of the relatively electron-poor vinyldiazoacetate A and the gold catalyst generates the gold-carbenoid B, which would be quickly attacked by the relatively electron-rich vinyldiazoacetate C (with stronger nucleophilicity), thus leading to the newly formed CÀC bond and giving rise to the intermediate D.…”

“…Following the pioneering research on copper-and ruthenium-catalyzed intermolecular coupling of diazo compounds toward simple alkenes (Scheme 1 A), [3,7] a breakthrough was made by Davies et al, who reported rhodium(II)-catalyzed cross-couplings of diazo compounds to selectively produce E-configured trisubstituted alkenes for synthetically useful applications (Scheme 1 B). [8] However, no significant progress has been made since then, especially for the synthesis of tetrasubstituted alkenes through diazo coupling. Therefore, it would be useful if practical procedures could be established to this end.…”

“…As a result, the desired product 4 d was obtained in 82 % yield and 2 d' (both Z and E isomers) was not detected. In contrast, treatment of 2 d with [Rh 2 (OPiv) 4 ] [8] did not afford 2 d' but instead delivered pyrazole as the sole product (Scheme 2). [16d, 19] Given this newly established protocol, various vinyldiazoacetates were subjected to this one-pot procedure [a] Reaction conditions: 1 and 2 (1 mmol each) in 5 mL of DCE was added slowly to IPrAuNTf 2 /NaBAr F (5 mol %) in 5 mL of DCE at RT.…”

Recent Developments in Coinage Metal Catalyzed Transformations of Stabilized Vinyldiazo Compounds: Beyond Carbenic Pathways

“…In contrast, the rhodium‐catalyzed cross‐coupling of vinyldiazoacetates and simple diazoacetates led to functionalized dienes as nicely disclosed by Davies and coworkers …”