The phosphine-catalyzed [4 + 2] annulations between allenoates and electron-poor trifluoromethyl ketones or N-tosylbenzaldimine dipolarophiles have been investigated in continuum solvation using density functional theory (DFT) calculations. The detailed reaction mechanisms as well as the high cis-diastereoselectivities of the reactions have been firstly clarified. Our calculated results reveal ...

The thermal reaction of trans-1-methyl-2,3-diphenylaziridine (trans-1a) with aromatic and cycloaliphatic thioketones 2 in boiling toluene yielded the corresponding cis-2,4-diphenyl-1,3-thiazolidines cis4 via conrotatory ring opening of trans-1a and a concerted [2þ 3]-cycloaddition of the intermediate (E,E)-configured azomethine ylide 3a (Scheme 1). The analogous reaction of cis-1a with dimethyl...

Carbonyl ylides are generally non-isolable reactive intermediates and have been extensively utilized as the dipole in 1,3-dipolar cycloaddition reactions with electron-deficient and electron-rich dipolarophiles to afford polycyclic compounds including five-membered oxacycles. The most efficient method for generating the carbonyl ylide is the interaction of a metal carbene complex with the oxyge...

Cycloaddition reactions are among the most powerful methods for the synthesis of complex compounds. In particular, the development and application of the 1,3-dipolar cycloaddition, an important member of this reaction class, has grown immensely due to its powerful ability to efficiently build various five-membered heterocycles. Azomethine ylides are commonly used as dipoles for the synthesis of...

Intermediates (trimethylenes) formed upon bond cleavage of three-membered rings are usually too unstable for direct characterization. They may. however. he stabilized by substitution and by incorporation into a cyclic system where the ring closed form is strained and conrotatory closure of the trimethylene is inhibited. These principles have been applied to two heterobicyclo[2.l .O]pentane syst...