Novel Hybrid Prins/Aza-Prins Oxocarbenium/N-Acyliminium Cascade: Expedient Access to Complex Indolizidines

Autotandem Catalysis: Inexpensive and Green Access to Functionalized Ketones by Intermolecular Iron-Catalyzed Amidoalkynylation/Hydration Cascade Reaction via N-Acyliminium Ion Chemistry

Iron-based catalysts were applied in cascade-type reactions for the synthesis of different carbonyl compounds. The reactions proceeded by a new iron-catalyzed cascade of alkynylation/hydration by using both the σ- and π-Lewis acid properties of iron salts. The alkynylation reactions of several endo and exocyclic acetoxylactams were achieved with three different catalysts including FeCl 3 .6H 2 O, FeCl 3 , and Fe(OTf) 3 showing the efficiency of σ-Lewis acidity of iron (III) salts in catalyzing the alkynylation reaction. We also demonstrated that the reaction sequence could be shortened by the direct use of hydroxylactams, leading to an environmentally friendly protocol, avoiding the need to perform unnecessary lengthy steps. A combination of the hard/soft iron Lewis acid properties was then used to implement an unprecedented tandem intermolecular alkynylation/intramolecular hydration sequence allowing expedient access to a new carbonyl structures from trivial materials.

Aza-heterocyclic frameworks through intramolecular π-system trapping of spiro-N-acyliminiums generated from isoindolinone

Spiro-acetoxylactams, obtained easily by the tandem carbonyl reduction/O-acylation, were submitted to acids giving through π-cationic cyclization aza-heterocyclic systems including amino-acids.

Access to 3-spiroindolizines containing an isoindole ring through intra-molecular arylation of spiro-N-acyliminium species: a new family of potent farnesyltransferase inhibitors

Based on N-acyliminium species, two efficient and rapid approaches to diversify spirocyclic systems connected by two different carbon centers to the isoindole ring have been developed. The imide reduction and the tandem oxidative cleavage of olefin/formyl-amide equilibration were at first selected as the key steps for these strategies. Ultimately the intramolecular α-amidoalkylation reaction was achieved through the arylation of α-acetoxy lactams or α-hydroxy lactams using, respectively, a Lewis acid or a Brønsted acid depending on the nature of N-acyliminium precursors. The latter led, in addition to the spiro-6-membered aza-heterocycles, to the formation of scarce spiro-5-membered analogues which show promising inhibitory activities on human farnesyltransferase in the nanomolar range demonstrating improved IC50 values of up to 1.5 nM.

Microwave-Assisted aza-Friedel-Crafts Arylation of N-Acyliminium Ions: Expedient Access to 4-Aryl 3,4-Dihydroquinazolinones

A one-pot microwave-assisted aza-Friedel-Crafts arylation of N-acyliminium ions, generated in situ from o-formyl carbamates and different amines, is reported. This metal-free protocol provides rapid access to diverse 4-aryl 3,4-dihydroquinazolinones in excellent yield without any aqueous workup. A solvent-directed process for the selective aza-Friedel-Crafts arylation of electron-rich aryl/heteroaryl/butenyl-tethered N-acyliminium ions is also described.