A novel synthesis of .beta.-lactams

Structure of a β-lactam, 2,6a-di-p-tolyl-6,6a-dihydro-3H,5H-azeto[2,1-b]imidazol-5-one, C19H18N2O

“…2. These results are in agreement with the expected formula (I), thus confirming the validity of the novel synthesis of Alper et al (1981). The five-membered ring is best described as having the twist form (T) with puckering parameters q2 = 0.146 (7) ,/~ and % = 261.3 (5) ° (Cremer & Pople, 1975).…”

Transition-Metal-Catalyzed Cleavage of C–N Single Bonds

“…As reported by Alper et al, bicyclic β-lactams 383 could be generated from 2H-azirines and CO in the presence of a catalytic amount of Pd(PPh 3 ) 4 (Scheme 112). 304,305 In the catalytic cycle, the reactive Pd species 384 is generated from Pd(PPh 3 ) 4 Park et al developed a rhodium carbenoid-mediated ringopening of 2H-azirines to construct substituted pyridines 396 (Scheme 114). 308 A variety of 2H-azirines with both electronrich and electron-deficient substituents could react smoothly with a series of diazo compounds to give the corresponding pyridines 396.…”

Palladium‐Catalyzed Dearomative Cyclocarbonylation by CN Bond Activation

“…However,w hen other leaving groups,s uch as NPh 2 ,N Bn 2 , OH, OAc, or Cl, were installed in the allylic skeleton, the conversion was dramatically lower under identical reaction conditions (entries [4][5][6][7][8]. Thelower activity of these substrates might be attributed to either the difficult cleavage of the corresponding CÀXb onds or their reluctance to undergo alate-stage Heck reaction.…”

“…[4] Among many efficient methods,t he carbonylation of C À Nb onds, astrategy that involves transition-metal-catalyzed C À Nbond activation followed by insertion of CO to furnish the amide group,has proven to be one of the most direct and promising ways to access ar ange of valuable amides. [5] Allylamines are suitable substrates for such catalytic processes,a st hey can smoothly undergo oxidative addition with Pd 0 to cleave the C À Nb ond for the generation of a p-allylpalladium species I and have thus been successfully applied in Pd-catalyzed aminocarbonylation reactions in the presence of CO (Scheme 1a).…”