Reactions with vinylnitroso compounds

One report has described the use of thiocarbonyl compounds as the he-terodienophile 2tt component of a Diels-Alder reaction with vinylnitroso compounds.80... 

Work has recently appeared on the synthesis and cycloaddition reactions of vinylnitroso compounds. - Although these compounds are capable of acting either as heterodienes or as nitroso dienophiles, their reactivity is critically dependent on their structure. In general, if the vinylnitroso system contains any )8 substituents, the compounds will react as dienophiles if there is no /3 substituent, the system prefers to act as the 4tt component of a Diels-Alder reaction and will react with dienophiles. 

An extensively investigated and useful hetero-2-azadiene system capable of 4it participation in Diels-Alder reactions is the vinylnitroso compounds.75-78 The complementary addition of electron-withdrawing substituents to the 3 position of the vinylnitroso system enhances the rate of diene participation in inverse electron demand Diels-Alder reactions with electron-rich or neutral dienophiles (simple olefins).75,76 Table 9-IV summarizes a series of representative examples of the 47r participation of vinylnitroso compounds in Diels-Alder reactions, and an extensive review has summarized much of this work.5,75... 

Vinylnitroso compounds may act as 2tt or 47t components of Diels-Alder reactions with typical dienes [Eq. (37)]. 

Of the four possible pathways, it has been empirically determined that vinylnitroso compounds bearing (3 substituents participate as 2ir dienophile components in Diels-Alder reactions with dienes [Eq. (37), path b]6 78 whereas vinylnitroso compounds lacking (3 substitutents participate as 47t diene components in their Diels-Alder reactions with dienes [Eq. (37), path a].6-76 The potential that the observed 47t participation of vinylnitroso compounds in Diels-Alder reactions with dienes [Eq. (37), path c] may arise from a sequence initiated by the all-carbon Diels-Alder reaction [Eq. (37), path d] followed by a [3,3]-sigmatropic rearrangement to the observed oxazine product [Eq. (38)]... 

Oxazines. - =-Nitrosostyrenes(320 R = Ar) form cycloadducts with alkenes to give 3-aryl-5,6-dihydro-4H-1,2-oxazines (321 R1 = Ar) vinylnitroso compounds similarly form 1,2-oxazines by addition to alkenes. These cycloaddition reactions are in general both regio-and stereo-selective. The nitroso compounds are generated in situ by treatment of the corresponding halogeno-oximes (319) with base.26 ... 

---