Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

Abstract

SummaryThe hetero-Diels–Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2H-1,2-oxazine scaffold is useful for the synthesis of many biologically interesting molecules due to the diverse opportunities created by subsequent transformations of the resulting 1,2-oxazine ring. This review discusses the rationale for the observed regio- and stereoselectivity and the methods developed in recent years used to control and improve the stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds.

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

“…A diene in which one of the two olefinic double bonds is internal, 1,3‐pentadiene ( 2 d ) still allowed the reaction to proceed efficiently (entry 24). 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 ,. 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 25–27).…”

The Application of 1,2-Oxazinanes as Chiral Cyclic Weinreb Amide-Type Auxiliaries Leading to a Three-Component, One-Pot Reaction

“…However, the low reactivity of the trisubstituted 1,3-diene in the NDA reaction led to an exclusive regioselectivity for the distal regioisomer 4d . 9a 13 As expected, several tetrasubstituted 1,3-dienes ( 5e – h ) remained unreactive in the acyl NDA reaction, presumably because the steric hindrance exerted by the substituents prevented the necessary s- cis conformation for the concerted NDA reaction from being adopted.…”

Ion mobility spectrometry-tandem mass spectrometry strategies for the on-line monitoring of a continuous microflow reaction

“…In organic chemistry, a wide range of biologically active compounds are synthesised by (hetero-) DA reactions. In particular, the formation of 1,2-oxazine compounds is of special interest to synthesise bioactive products or stabilize them and selectively functionalize natural products [21][22][23]. The 1,2-oxazine compounds are formed as a result of nitroso dienophile reaction with conjugated diene.…”