Ring transformations of 3-(diethylamino)-5-chloro-2(1H)-pyrazinones and the corresponding 2H-1,4-oxazin-2-ones on reaction with acetylenic compounds

A Novel Diels-Alder Approach To Heavily Substituted Azasugars

“…20 Starting from cyanohydrins, Hoornaert prepared various 6-substituted 3,5-dichloro-1,4-oxazin-2-ones and subsequently demonstrated that they undergo [4+2] cycloaddition with concomitant loss of CO 2 or cyanogen to afford pyridines 21 and 2H-pyran-2-ones, respectively. 22 Later, Hoornaert demonstrated that 2-oxa-5-azabicyclo[2.2.2]oct-5-en-3-one cycloadducts can also be isolated from the cycloadditions 23 and reported on their chemical manipulation. 24 These observations by Hoornaert encouraged us to consider a route to substituted piperidines from the cycloaddition of 1,4-oxazin-2-ones.…”

3,5-Dihalo-2(1H)-pyrazinones: Versatile Scaffolds in Organic Synthesis

“…Diels-Alder reactions of the 2-azadiene system of 2(1H)pyrazinones have been extensively studied by the Hoornaert group. 16,17,24,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] Diels-Alder reactions on pyrazinones, both with alkynes and alkenes, provide an interesting method for the synthesis of different heterocyclic systems and synthetic building blocks.…”

“…Cycloadducts of 3-amino substituted 2(1H)-pyrazinones 75 with alkynes do not undergo the normal cycloreversion process; instead, rearranged compounds of type 79 are obtained (Scheme 23). 24,32,34 As far as we know, only one example has been reported of a Diels-Alder reaction of pyrazinone with a heterodienophile (p-toluenesulfonyl cyanide) (Scheme 24). 46…”

Cyclobutenedione-Based Method for the Synthesis of Substituted 2-Pyridinones and Dihydro-2-pyridinones

“…Representative synthetic routes have been developed by Junjappa, , Chuit, and Cainelli . 2-Pyridinones have also been synthesized through a variety of cycloaddition procedures. ,− Although a variety of methods for the preparation of substituted 2-pyridinones have been reported, new, concise, regioselective, and functional-group-tolerant methods are continuously being sought.…”