Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

Abstract

[Bis(trifluoroacetoxy)iodo]benzene (BTI) and (diacetoxyiodo)benzene (DIB) efficiently promote the formation of acylnitroso species from hydroxamic acids in the presence of various dienes to give the corresponding hetero-Diels–Alder (HDA) adducts in moderate to high yields. The present method could be applied to the HDA reactions of acylnitroso species with o-benzoquinones generated by the oxidative dearomatization of guaiacols.

Phenyliodine(III)diacetate (PIDA): Applications in Organic Synthesis

“…1,2-Oxazines can be easily and highly stereoselectively synthesized using the hetero-Diels-Alder (HDA) reaction between N-acylnitroso species and dienes. In the presence of different dienes (61), either PIDA or [bis(trifluoroacetoxy)iodo]benzene (BTI) effectively stimulated the production of acylnitroso species (62) from hydroxamic acids (60), yielding the required hetero-Diels-Alder (HDA) adducts in moderate to high yields, as reported by Saito and co-workers [24]. The current approach could be used in HDA reactions involving masked o-benzoquinones (MOBs), which are produced after the oxidative dearomatization of guaiacols, as well as simple dienes (Scheme 10).…”

Development of New Reactions Driven by N–O Bond Cleavage: from O-Acyl Hydroxylamines to Tetrodotoxin

“…sought to evaluate a distinct approach in which a different C4a aldehyde surrogate was employed. 49,50 This second-generation approach is marked by the use of a dimethyl ketal 59 as a latent ketone, enabling us to leverage prior results on the nitroso Diels-Alder cycloadditions of masked ortho-benzoquinones, 51,52 versatile intermediates in the synthesis of complex natural products derived from phenolic feedstocks such as guaiacol 60 (Scheme 16a). 53 We synthesized diene 61 in ten steps from 2-bromophenol.…”

Cross‐Dehydrogenative Coupling Reactions between Phenols and Hetarenes: Modern Trends in Cross‐Coupling Chemistry of Phenols

“…The simplest method of implementing this approach is by adding a methanol molecule to 2‐ or 4‐methoxyphenol in the presence of PIDA to form o ‐ or p ‐benzoquinone monoketal (Scheme 2), which can further be used in the cycloaddition reaction [17–24] …”

“…[14] The simplest method of implementing this approach is by adding a methanol molecule to 2-or 4-methoxyphenol in the presence of PIDA to form o-or pbenzoquinone monoketal (Scheme 2), which can further be used in the cycloaddition reaction. [17][18][19][20][21][22][23][24] In 1999, Liao and co-workers reported reactions of indoles with in situ generated o-benzoquinonone monoketals, also referred to as 'masked o-benzoquinones' (MOBs), possessing an electron-withdrawing group (EWG). [24] The use of 3-substituted indoles in the reaction with MOBs in the presence of PIDA and methanol produced the Diels-Alder products (Scheme 3i) in moderate yields.…”