Synthesis of Spiro Ketals, Orthoesters, and Orthocarbonates by CpRu-Catalyzed Decomposition of α-Diazo-β-ketoesters

Abstract

Reactions of α-diazo-β-ketoesters with cyclic ketones, lactones, and carbonates are reported. Thanks to the combined use of salt [CpRu(CH3CN)3][BArF] and 1,10-phenanthroline as catalyst for the diazo decomposition, effective and practical syntheses of spiro bicyclic ketals, orthoesters, and orthocarbonates are afforded.

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

“…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] . Using α‐diazo‐β‐ketoesters as reagents, carbonyl ylides evolve toward the formation of dioxolene adducts instead that are formed by intramolecular condensation ( A , path d ) [31–38] . While such a process occurs quite readily with aldehydes and ketones, but also with esters (lactones) and cyclic carbonates, [32] examples of dioxolene formation with amide functional groups are rare.…”

“…Using α‐diazo‐β‐ketoesters as reagents, carbonyl ylides evolve toward the formation of dioxolene adducts instead that are formed by intramolecular condensation ( A , path d ) [31–38] . While such a process occurs quite readily with aldehydes and ketones, but also with esters (lactones) and cyclic carbonates, [32] examples of dioxolene formation with amide functional groups are rare. In fact, the only reported examples of corresponding amide acetals have been reported by Heimgartner , Nikolaev and collaborators using succinimide derivatives as substrates ( Scheme 1, B ) [39–41] .…”

Preparation and Structural Characterization of [CpRu(1,10‐phenanthroline)(CH3CN)][X] and Precursor Complexes (X=PF6, BArF, TRISPHAT‐N)

“…[49] This catalytic system also promotes condensation reactions with nitriles, ketones, aldehydes and more recently with lactones and cyclic carbonates to generate the corresponding heterocycles (Scheme 1). [49,50] Finally, in recent studies, regio and synstereoselective three-atoms insertions into a large variety of epoxides and oxetanes were described leading to the formation of original 1,4-dioxene and 1,4-dioxepine motifs respectively with, as pre-catalyst, the [CpRu…”

“…This catalytic system also promotes condensation reactions with nitriles, ketones, aldehydes and more recently with lactones and cyclic carbonates to generate the corresponding heterocycles ( Scheme 1). [49,50] Finally, in recent studies, regio and syn ‐stereoselective three‐atoms insertions into a large variety of epoxides and oxetanes were described leading to the formation of original 1,4‐dioxene and 1,4‐dioxepine motifs respectively with, as pre‐catalyst, the [CpRu(CH 3 CN) 3 ][BAr F ] (BAr F =tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate) specifically [51,52] . In view of the influence played by the BAr F or PF 6 anion nature onto the [CpRu] reactivity [44] but also, more generally, of the importance of negative counterions in catalysis, [53–55] care was then taken to determine the structural impact associated such counterions onto [CpRu(1,10‐phenanthroline)(CH 3 CN)][X] and precursor complexes 1…”

Functionalizing the γ-position of α-diazo-β-ketoesters

“…These compounds are prepared from β-ketoesters via diazo transfer reactions 1 and are valuable intermediates in the synthesis of heterocyclic systems, notably including the synthesis of carbapenems as shown in Scheme 1. 2 The stabilized diazo group is capable of selective, and directed, activation with transition metals, including Rh II , especially Rh 2 (OAc) 4 and Rh 2 (esp) 2 , 3 Cu I , 4 Cu II , 5 Ru II , 6 as well as Rh III , 7 Ir III , 8 and Co III , 9 to affect a wide array of intramolecular and intermolecular insertion reactions (N-H, 10 O-H, 11 and C-H 12 ) and addition of the carbenoid to alkenes. 13 The diazo functionality is also susceptible to strongly electrophilic reagents under non-catalytic, conditions, including reactions with bromine and dimethyldioxirane, as shown in Scheme 2.…”