Metal-catalyzed reactions between α-diazo esters and imines were well-known to yield aziridine derivatives exclusively. This work reports two new olefination reactions between N-Boc-derived (Boc = tert-Butyloxycarbonyl) imines and α-diazo esters with Ag(I) and Au(I) catalysts, respectively. Our mechanistic studies reveal that these new olefinations involve an initial attack of diazo esters on metal/ imine complexes to form Mannich-addition intermediates, which subsequently afford α-aryl-β-aminoacrylates via a Roskamp reaction, or to form β-aryl-β-aminoacrylates via the formation of silver carbenes. α-Diazo carbonyl compounds have found widespread applications in organic synthesis, because they readily form reactive metal carbenes. 1 These metal carbenes undergo various and useful transformations such as X−H insertions (X = C, N, O, S, Si), cyclopropanation, Stevens and Wolff rearrangements, and ylide-based cycloaddition reactions. 2 Equation 1 (Scheme 1) shows one well-known system for catalytic [2 + 1] annulations of numerous imines with diazo esters via α-oxo metal carbenes (In-1) that are subsequently captured by nucleophilic imines to yield aziridine products. 3 Such aziridine syntheses have been achieved with less acidic metal catalysts including Rh(II), Ru(II), Cu(I), Re(I), and Co(II). Alternatively, in the case of Brønsted acids and BF 3 , 4 diazo esters serve as nucleophiles to attack metal/imine pairs to form intermediates of Mannich type (In-2), which also afford aziridines preferably (Scheme 1, eq 2). Equation 3(Scheme 1) highlights one specific example that employs (R)-VANOL to catalyze an asymmetric [2 + 1] annulation of N-Boc-derived (Boc = tert-Butyloxycarbonyl) imines with α-diazo esters; 4h herein, α-aryl-β-aminoacrylate was formed also in small proportions, indicative of an unknown path. We are aware of no example to obviate this aziridine chemoselectivity unless α-diazo esters are replaced with α-diazo nitriles. 5 In seeking new chemoselectivity beyond aziridine formation, this work reports two new olefinations between α-diazo esters and N-Boc-derived imines using Au(I) or Ag(I) catalysts without additive. With a cationic Au(I) catalyst, these imine/α-diazo ester mixtures yield α-aryl-β-aminoacrylates, involving a Roskamp reaction 6 of intermediates In-2′, whereas a Ag(I) catalyst enables the same intermediates to afford β-aryl-βaminoacrylates via silver carbene intermediates. Our mechanistic analysis supports the roles of intermediates ln-2′ that have been verified with deuterium labeling and other control experiments.Importantly, these two new catalytic reactions are accessible to two β-amino acrylates with the same imines and α-diazo esters; these functionalized acrylates are recognized as useful building blocks to construct numerous heterocyclic rings