Oxidative Spirocyclization of Phenolic Sulfonamides: Scope and Applications

Abstract

A full account of the oxidative dearomatization of para‐ and ortho‐phenolic sulfonamides is provided together with an overview of the chemistry of the products and their elaboration to building blocks for spirocyclic alkaloids. A concise total synthesis of putative lepadiformine complements the discussion.

Synthesis of Benzannulated Medium‐ring Lactams via a Tandem Oxidative Dearomatization‐Ring Expansion Reaction

“…The phenol in the original substrate system (Figure b) was replaced with an aryl bromide to avoid competing oxidative activation of the phenol. Indeed, Ciufolini has reported extensive studies of such oxidative dearomatization reactions of phenols in the presence of nitrogen nucleophiles under the ‘normal“ polarity reaction manifold . We postulated that umpolung oxidative dearomatization would provide a cyclohexadienyl bromonium intermediate 2 a in situ, which could then undergo spontaneous ring‐expanding rearomatization to form a C1 tertiary carbocation, providing the olefin 3 a after E1 elimination .…”

Highly Stereoselective Metal‐Free Oxyaminations Using Chiral Hypervalent Iodine Reagents

“…[1,2] They are used in a wide range of transformations as environmentally friendly, mild and highly selective oxidants because they avoid the issues of toxicity or the complicated ligands of many transition-metal-based systems. They can also be employed as electrophilic reagents for the functionalization of alkenes in halolactonizations [3] and dioxytosylations, [4] for the oxidative dearomatization of phenols, [5] and the a-functionalization of ketones. [6,7] In this context, the use of chiral hypervalent iodine reagents for asymmetric transformations has emerged as an interesting area of research in recent years.…”

Saccharide Recognition and Helix Formation in Water with an Amphiphilic Pyridine–Phenol Alternating Oligomer

“…Scheme shows the synthesis of target oligomer 1 . The three starting materials, 4‐(3‐hydroxypropyl)phenol ( 2 ), heptaethylene glycol monomethyl ether p ‐toluenesulfonate ( 5 ), and 2,6‐diiodo‐4‐(1,4,7,10,13,16,19,22‐octaoxatricosanyl)pyridine ( 12 ), were prepared by literature procedures. Oxidative iodination[8b] of 2 gave diiodide 3 , of which the hydroxy group was protected with an methoxymethyl (MOM) group to yield 4 .…”