Hetero‐Diels‐Alder‐Reaktionen von Nitrosocarbonylverbindungen als nützliches Verfahren in der organischen Synthese

Abstract

Organische Transformationen, die in einem einzigen Reaktionsschritt mehrere kovalente Bindungen aufbauen, zählen zu den leistungsfähigsten Verfahren in der organischen Synthese. Hetero‐Diels‐Alder(HDA)‐Reaktionen von Nitrosocarbonylverbindungen ermöglichen die stereospezifische Einführung von Kohlenstoff‐Stickstoff‐ und Kohlenstoff‐Sauerstoff‐Bindungen in einem einzigen Syntheseschritt und bieten einen direkten Zugang zu 3,6‐Dihydro‐1,2‐oxazinen. In diesem Aufsatz werden die Entwicklung der Nitrosocarbonyl‐HDA‐Reaktion und der Nutzen der daraus erhältlichen Oxazinringe bei der Synthese verschiedener wichtiger biologisch aktiver Verbindungen beschrieben.

Regio‐ and Stereochemical Studies on the Nitroso‐Diels–Alder Reaction with 1,2‐Disubstituted Dienes

“…[1] Amongst these reactions, the nitroso-Diels-Alder reaction has been the subject of intense studies and has found many applications in the synthesis of various natural products. [2] Since the introduction of the first nitroso-Diels-Alder by Wichterle in 1947, [3] several nitroso reagents have been designed for the reaction, the most important ones being arylnitroso, chloronitroso and acylnitroso reagents, which possess different stabilities and reactivities. Recently, we have also introduced acetoxynitroso derivatives as stable and easy-to-handle chloronitroso surrogates [4] (Figure 1).…”

Gold‐catalyzed [4+2] Annulations of Dienes with Nitrosoarenes as 4 π Donors: Nitroso‐Povarov Reactions

“…Nitrosoarenes are very versatile and undergo metal-catalyzed cycloadditions [1,2] with p-bond motifs including dienes, [2] alkynes, [3] and allenes. [4] These cycloadditions are accessible to valuable 1,n-aminoalcohols through reductive cleavage of the weak N À Obonds of cycloadducts.Catalytic [4+ +2] cycloadditions of dienes with nitrosoarenes represent one of the most successful reactions in metal catalysis because of their facile access to 1,4-aminoalcohols in high diastereo-and enantiomeric purity [Scheme 1, Eq.…”

“…(1)]. [1,2] We are aware of no examples wherein nitrosoarenes serve as 4 p donors in catalytic annulations,a lthough [4+ +2] cycloadditions between transient nitrosoalkenes and electron-rich alkenes are well known [Eq. (1)].…”

Rhodium(II)‐ and Copper(II)‐Catalyzed Reactions of Enol Diazoacetates with Nitrones: Metal Carbene versus Lewis Acid Directed Pathways

“…[2] Of particular interest are the 3,6-dihydro-1,2-oxazines, which are available through nitroso hetero-Diels-Alder reactions, [3] gold-catalyzed cycloisomerization with allenes, [4] or (for selected examples) by a one-pot organocatalytic process involving a-oxyamination and an intramolecular Wittig reaction. [2] Of particular interest are the 3,6-dihydro-1,2-oxazines, which are available through nitroso hetero-Diels-Alder reactions, [3] gold-catalyzed cycloisomerization with allenes, [4] or (for selected examples) by a one-pot organocatalytic process involving a-oxyamination and an intramolecular Wittig reaction.…”

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Access to 1,2-oxazines has proven to be highly valuable for the preparation of a multitude of biologically active target compounds, [1] but there are few methods that have been developed for their syntheses. [2] Of particular interest are the 3,6-dihydro-1,2-oxazines, which are available through nitroso hetero-Diels-Alder reactions, [3] gold-catalyzed cycloisomerization with allenes, [4] or (for selected examples) by a one-pot organocatalytic process involving a-oxyamination and an intramolecular Wittig reaction. [5] These oxazines have been valued as synthetic building blocks in organic syntheses, [6] and they are frequently found as structural skeletons in biologically active compounds.

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