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

Abstract

The synthesis of spirocyclic amide acetals (33–93 %) has been achieved through Ru(II)‐catalyzed condensations of N‐carbamate protected pyrrolidinones with metal carbenes derived from α‐diazo‐β‐ketoesters. Thanks to the mildness of the diazo decomposition conditions induced by a 1 : 1 combination of [CpRu(MeCN)3][BArF] and 1,10‐phenanthroline, the formation of the sensitive products is possible. Full characterization of this carbonyl‐ylide mediated process is provided by DFT calculations.

Chemo‐ and Regioselective Multiple C(sp2)−H Insertions of Malonate Metal Carbenes for Late‐Stage Functionalizations of Azahelicenes

“…To ensure a full mechanistic picture, the formation of 3 a , r‐3 a and 4 aa products was calculated with both catalytic conditions. The results for the formation of r‐3 a and 3 a are summarized in Figure 4, left and right panels, respectively, using malonate carbene complexes I0 as starting points [30] . The same mechanism applies for both Ru and Rh mediated reactions although with important energetic differences.…”

“…The results for the formation of r‐3 a and 3 a are summarized in Figure 4 , left and right panels, respectively, using malonate carbene complexes I0 as starting points. [30] The same mechanism applies for both Ru and Rh mediated reactions although with important energetic differences. In the case of 3 a , four key series of steps are observed: (1) a metal‐carbene addition to the C(sp 2 )−H bond, (2) two subsequent proton transfer steps (CH→OH and then OH→NH), (3) a migration of the metal from the reactive carbon to an O‐coordination, and (4) a final NH→CH proton transfer step to deliver target 3 a after catalyst regeneration.…”

Mechanistic insights into catalyst-dependent divergent cycloaddition reactionsviadiscrimination between diazo compounds

“…This kind of compound has been previously observed as the product from a carbonyl ylide dipole via proton transfer by Padwa and co-workers. 25–27 Although the earliest example of a similar process was reported in 1953 and many related cases have been proposed, 28–32 the mechanisms for the formation of the cyclic ketene N , O -acetal remain unclear.…”