BF3·Et2O-Catalyzed Formal [3 + 2] Reaction of Aziridinofullerenes with Carbonyl Compounds

Electrochemical tandem trifluoromethylation of allylamines/formal (3 + 2)-cycloaddition for the rapid access to CF3-containing imidazolines and oxazolidines

A straightforward and environmentally friendly synthesis of CF₃-containing imidazolines and oxazolidines has been developed through an electrochemical three-component reaction among allylamines, the Langlois reagent, and nitrile or carbonyl compounds.

Unusually Facile Thermal Homodienyl-[1,5]-Hydrogen Shift Reactions in Photochemically Generated Vinyl Aziridines

A range of photochemically generated tri- and tetracyclic vinyl aziridines have been found to undergo a general and surprisingly low temperature ring opening through a [1,5]-hydrogen shift reaction. The rate of the process was found to be highly dependent on the structure and substitution around the azirdine ring and the alkene terminus, with some substrates being observed to undergo ring opening at temperatures as low as 25 °C. The rigid nature of these polycyclic systems precludes a conformational explanation of these rate differences, and an Eyring study confirmed a negligible entropic barrier to the reaction. However, the Eyring plots for two different aziridines systems showed a significant difference in their enthalpies of activation. It is therefore believed that the levels of aziridine ring strain, as well as electronic effects, are the dominant factors in this sequence.

Combining photochemistry and catalysis: rapid access to sp3 - rich polyheterocycles from simple pyrroles

Use of FEP flow reactor technology allows access to gram quantities of photochemically-generated tricyclic aziridines. These undergo a range of novel palladium-catalyzed ring-opening and cycloaddition reactions, likely driven by their inherent strain, allowing incorporation of further functionality by fusing additional heterocyclic rings onto these already complex polycyclic cores. This rapid, 2-step access to complex sp3 - rich heterocycles should be of interest to those in the fields of drug discovery and natural product synthesis.

Studies on the formal [3 + 2] cycloaddition of aziridines with alkenes for the synthesis of 1-azaspiroalkanes

The Lewis acid-mediated [3 + 2] cycloaddition of N-sulfonyl- and N-sulfamoylaziridines with alkenes provides a rapid and efficient access to 1-azaspiro[4.n]alkanes. Experimental studies have been combined with DFT calculations to explore the mechanism of the reaction. They demonstrate that the nature of the electron-withdrawing nitrogen protecting group has a very limited influence on the course of the reaction and, particularly, on the initial formation of the 1,3-zwitterionic species through C-N bond cleavage, which has been found to be the rate-determining step. Compared to N-sulfonylaziridines, N-sulfamoylaziridines have proved to be more synthetically useful synthons that afford crystalline polycyclic structures in good yields. A short sequence of catalytic C(sp(3))-H amination-cyclization-[3 + 2] cycloaddition has then been successfully designed to afford the homologue 1-azaspiro[5.n]alkanes, thereby illustrating the higher versatility of sulfamates in these cycloadditions.

Cu(OAc)2-promoted reaction of [60]fullerene with primary amines or diamines

The Cu(OAc)₂-mediated oxidative dehydrogenative addition of easily available primary amines to C₆₀ allows the concise preparation of aziridinofullerenes. Moreover, the Cu(OAc)₂-promoted reaction of C₆₀ with diamines affords C₆₀-fused cyclic 1,2-diaminated fullerenes.

TsOH-mediated reaction of aziridinofullerene with diols for the preparation of fullerene-fused dioxygenated ring compounds

Reaction of aziridinofullerene with diols promoted by p-toluenesulfonic acid affords various fullerene-fused dioxygenated ring compounds with six- to ten-membered heterocycles.