Additionsreaktionen der nitrosogruppe—VI

Synthesis of 3,6‐Dihydro‐2H‐[1, 2]‐Oxazines from Nitroarenes and Conjugated Dienes, Catalyzed by Palladium/Phenanthroline Complexes and Employing Phenyl Formate as a CO Surrogate

“…Moreover, even the second aspect is important, as the nitrosoarene is involved in a hetero Diels-Alder reaction and the latter is well known to proceed the better the lower is the level of the orbitals of the dienophile. [25] The presence of a para methoxy group on the aryl ring of nitrosobenzene allows a quinonoid resonance form for 1 n, where the nitroso group gain a negative charge and loses its double bond, making it unsuitable to undergo a Diels-Alder reaction (Scheme 2). [26] Although no resonance structure can be drawn in the case of 4-nitrobenzoate anion, it is clear that the deprotonation of 1 i by triethylamine both decreases the reactivity of the nitro compound and the tendency of the intermediately formed nitroso arene to be involved in a hetero Diels-Alder reaction, thus explaining the low yield obtained with this substrate.…”

“…Again two isomers were formed, but in this case the proximal isomer prevailed (3 bdA/3 bdB = 0.75 : 1) in accord with what expected based on the literature for related oxazines. [7c,30] However, when dienes were employed in which both double bonds are internal (2 e-g) only trace amounts of the corresponding oxazines could be detected (entries [25][26][27]. One problem is that in these cases the formation of the oxazine is reversible at high temperature [11b] and the accumulated nitrosobenzene can be involved in side reactions, among which the formation of azoxyarenes appears to predominate in our system.…”

Fine Chemicals by Reductive Carbonylation of Nitroarenes, Catalyzed by Transition Metal Complexes

“…The other is that under CO pressure a competition exists between the hetero Diels-Alder reaction and a carbonylation reaction to afford diarylureas (or even carbamates, when the reaction is run in methanol). The hetero Diels-Alder reaction is known to be disfavored by electrondonating substituents on the aryl ring [64,65], whereas the reverse occurs for the CO insertion reaction leading to carbonylated products.…”

Photo‐induced iron‐catalyzed allylic amination of unfunctionalized olefins with nitroarenes

“…In fact, the nitrosoarene acts as an electrophile in the coupling with an olefin, and electronwithdrawing groups accelerate these kinds of couplings on the aromatic ring. 25,26 The product formation appreciably decreases with an in increase in temperature and a decrease in pressure (Table 1, runs 5 and 6). The GC detected only aniline as a major product when 3,4-dichloronitrobenzene and pentachloronitrobenzene were employed as N-transfer agents.…”