An expedient and concise Ugi-based unified approach for the rapid assembly of quinoxaline frameworks has been developed. This convergent and versatile method uses readily available commercial reagents, does not require advanced intermediates, and exhibits excellent bond-forming efficiency, thus exemplifying the operationally simple synthesis of quinoxaline libraries.
An expedient and concise Ugi-based unified approach for the rapid assembly of quinoxaline frameworks has been developed. This convergent and versatile method uses readily available commercial reagents, does not require advanced intermediates, and exhibits excellent bond-forming efficiency, thus exemplifying the operationally simple synthesis of quinoxaline libraries.
Concise two-step, one-pot protocols for the syntheses of quinoxalines and 5H-benzo[e][1,4]diazepines are reported. An acidless' Ugi reaction followed by a Boc-deprotection-cyclization sequence is shown to produce arrays of both functionalized scaffolds in good yield. Mono-N-Boc-protected diamines are employed to access quinoxalines and an analogous benzylic amine affords access to 5H-benzo[e][1,4]diazepines in conjunction with supporting reagents in the acidless' Ugi reaction. Both methodologies are robust, straightforward, and allow installation of at least three points of diversity in the resulting scaffolds.