and convenient synthesis of α‐allyl cyclic amidines has been achieved by applying a novel cascade reaction. Copper(I)‐mediated in situ N‐sulfonyl ketenimine formation from the reaction of a terminal alkyne with sulfonyl azide is followed by an intramolecular nucleophilic attack on the central carbon atom by an allylic tertiary amine, and then an aza‐Claisen rearrangement takes place through a chair
Ethyl N-(diphenylmethylene)glycinate as anionic glycine equivalent. Monoalkylation, dialkylation and Michael additions under solid-liquid phase-transfer catalysis
additions to ethylenic and acetylenic acceptors under appropriate solid-liquid phase transfer catalysis conditions. Further transformations of the α-disubstituted ketimines lead to α-alkylated aspartic and glutamic acid derivatives 10, 15, 19 and 26, to bicyclic amino acids or derivatives featuring pyrazolone and isoxazolone moieties 30 and 33, and to α-substituted (E)-3,4-dehydroglutamic acids.
Ethyl N-diphenylmethyleneglycinate reacts with one equivalent of alkylating agents in the presence of powdered potassium carbonate to afford, after hydrolysis, monoalkylated glycine esters. A similar process using two equivalents of alkylating agents in the presence of powdered potassium hydroxide and a phase transfer catalysts gives, after hydrolysis, dialkylated glycine esters.
Halogen bond: The choice of the iodoniumcomplex of pyridines, either IPy2PF6 or I(coll)2PF6 (Py=pyridine; coll=2,4,6‐trimethylpyridine), was crucial for controlling the iodocyclization/oxidation sequence of α‐propargylic glycine derivatives. This reagent‐controlled system enabled switchable access to 2,3‐dihydropyrroles and pyrroles (see scheme).