Chemistry of cyclopropanones. VI. New synthesis of .beta.-lactams

Ring-opening, cycloaddition and rearrangement reactions of nitrogen-substituted cyclopropane derivatives

“…374 More generally and as initially demonstrated by the group of H. Wasserman in the early 1970s, the activation of N-chlorocyclopropylamines by silver salts can lead to fourmembered ring rearranged products according to equation 8 (Scheme 3). 375 This method provides a synthetically useful access to β-lactams, starting from substrates that bear an oxygen atom on the cyclopropane ring at the α position relative to the nitrogen atom (Scheme 154). Similar rearrangements have been shown to be feasible with other leaving groups than the chloride ion: N 2 + (cyclopropylazide substrates, see paragraph 5.4.1), OBz 375 and OTs.…”

“…375 This method provides a synthetically useful access to β-lactams, starting from substrates that bear an oxygen atom on the cyclopropane ring at the α position relative to the nitrogen atom (Scheme 154). Similar rearrangements have been shown to be feasible with other leaving groups than the chloride ion: N 2 + (cyclopropylazide substrates, see paragraph 5.4.1), OBz 375 and OTs. 376…”

“…375,377,378,379,380 Typically, the N-chloroamines are obtained by N-chlorination of cyclopropane hemiaminals, which are prepared by the addition of amines onto cyclopropanone derivatives, and are then directly treated with silver(I). 375,377,378 This one-pot procedure has been applied to the In contrast, the reported ring-opening reactions of N-chlorocyclopropylamines substituted with a phenyl or a carboxylic acid group at the α position relative to the nitrogen atom yield linear products in the presence of methanol or water. While in the former case, the mechanism is proposed to involve again the initial formation of a cationic four-membered ring intermediate, 381 N-chlorinated aminocyclopropylcarboxylic derivatives, as electron-deficient substrates, are believed to undergo nucleophilic ring-opening.…”

Synthesis of 4,4-Disubstituted β-Lactams by Regiospecific Electrophile- and Silver-Induced Ring Expansion of 2,2-Disubstituted 1-Methoxycyclopropylamines

“…Some ring transformations to form β-lactams have been reported, the most appealing one being the ring expansion of amine adducts across cyclopropanones. − The addition of primary amines to cyclopropanone 1 afforded labile carbinolamines 2 which were suitable sources for β-lactams 3 via a synthetic procedure involving N-chlorination with tert -butyl hypochlorite and subsequent reaction with silver salts (Scheme ). , This elegant synthesis suffers from a major drawback, i.e. , the difficult accessibility of cyclopropanone, which is prepared by the low-temperature cycloaddition of diazomethane across ketene .…”

Íons nitrênio

“…Wasserman 44 desenvolveu uma rota Devido à maior eletronegatividade do átomo de nitrogênio é de se esperar que os íons nitrênio sejam mais reativos que os íons carbênio análogos, e que migrações internas de grupos alquila e hidreto, possam ocorrer com facilidade, interconvertendo íons nitrênio em íons carbênio. Desta forma, o melhor aproveitamento dos íons nitrênio em síntese orgânica seriam nas adições intramoleculares a sistemas π.…”