ABSTRACT
1,3-Dipolar cycloaddition of 2- and 3-nitrobenzaldehydes with 2-aminomethylpyridine and ethyl (2E)-2-cyano-3-(4-nitrophenyl)prop-2-enoate yielded endo-cycloadducts as the sole products under various reaction conditions. Fortuitously, 4-nitrobenzaldehyde behaved differently in three- and four-component cascades to produce a mixture of endo- and exo'-cycloadducts. This reaction is solvent- and temperature-dependent, and consequently, both the endo- and exo'-cycloadducts were synthesized in an excellent regio-, stereo-, and chemoselective fashion. Retro-1,3-dipolar cycloadditions of the endo-cycloadducts were conducted under mild reaction conditions, and the generated syn-dipoles were stereomutated into anti-dipoles which recycloadded with the dipolarophiles to provide the exo'-cycloadducts. Mechanistic studies were carried out to support the proposed mechanisms. Unprecedentedly, particular arylidene scaffolds participated as aldehyde or activated methylene precursors. Density functional theory calculations were performed to shed light on the importance of AcOH in the generation and isomerization of dipoles and to explain the high selectivity and the possibility of retro-cycloaddition.
ABSTRACT
Palladium catalysed three component cascade process, involving coupling of 2-iodobenzoates, -benzaldehydes, or acetophenones with substituted allenes and ammonium tartrate as an ammonium surrogate, provides a novel and facile route to substituted functionalised isoquinolinones and isoquinolines in good yields.
ABSTRACT
Catalytic 5-component cascade chemistry provides an effective stereo- and regioselective route to novel multi-functional Z,Z-bisallylamines. The process, which is capable of considerable further extension, utilises ammonium tartrate as a novel ammonia source which avoids the use of ammonia gas or aqueous ammonia.
ABSTRACT
3- And 9-component Pd(0) catalysed assembly of allenes, aryl iodides and N-nucleophiles with concomitant installation of trisubstituted Z-alkenes is readily achieved.
