Huan Liang

Chiral Hypervalent Iodine Reagents in Asymmetric Reactions

Hypervalent iodine reagents are unusually effective promoters of transformations that would be difficult, perhaps impossible, to accomplish otherwise. Low toxicity, a favorable safety profile, ease of handling, and an environmentally benign nature make them particularly attractive as agents for metal-free reactions. Their unique reactivity inspires the exploration of powerful new strategies that simplify the synthesis of complex molecules, as apparent from an ever increasing number of papers and reviews. A rapidly expanding area of research focuses on asymmetric transformations induced by chiral hypervalent iodine species. Activity in this field may be traced to a pioneering report on the enantioselective oxidation of sulfides to sulfoxides. Notable asymmetric reactions developed since include alkene dioxygenation, a oxygenation of ketones, and oxidative dearomatization of phenols (Scheme 1). Chiral reagents based both on I (l) and I (l) have been described, some of which may be conveniently generated in situ by oxidation of appropriate iodoarenes and used in a catalytic, substoichiometric, or excess amount. The chiral elements present in these agents are drawn either from the chiral pool or from scaffolds that have been extensively employed in transition-metal-catalyzed reactions (see examples in Scheme 2). The highest levels of asymmetric induction

Oxidative Spirocyclization of Phenolic Sulfonamides: Scope and Applications

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.

Improved Procedure for the Bimolecular Oxidative Amidation of Phenols

Trifluoroacetic acid (TFA) is an effective promoter of the bimolecular Ritter-like oxidative amidation of 4-substituted phenols induced by PhI(OAc) 2 in MeCN. This suppresses the need for fluoroalcohol cosolvents, increases the yields, and facilitates isolation/purification procedures.

Di-tert-butylisobutylsilyl, Another Useful Protecting Group

The di-tert-butylisobutylsilyl (BIBS) protecting group offers new possibilities for synthetic processes because of its steric bulk, robustness of its derivatives, and other special properties.

Synthetic Studies toward Sordarin: Building Blocks for the Terpenoid Core and for Analogues Thereof

Avenues to bi- and tricyclic building blocks for the elaboration of sordaricin and its analogues are described. The target molecules were obtained through inter- and intramolecular Diels-Alder reactions of a number of previously unknown cyclopentadienes. Unusual properties of 3-cyanoenones and 1-cyanocyclopentadienes have been unveiled and circumvented.

Progress towards the Synthesis of Sordarin and its Analogs

Introduction ..........................................................................................112 I. Total Syntheses of Sordaricin and of Sordarin...................................114 1. The Kato-Takeshita Synthesis of Sordaricin Methyl Ester .......................114 2. The Mander Synthesis of Sordaricin......................................................116 3. The Narasaka Synthesis of Sordarin......................................................119 II. Synthesis of Analogs of Sordarin.........................................................121 1. The Cuevas Sordarin Analogs ...............................................................121 2. The Ciufolini Synthesis of Sordarin Analogs..........................................123 III. Conclusion .............................................................................................129 Acknowledgements ...............................................................................129 References..............................................................................................130

10-Ethynyl-2,3,6,6a,9,10-hexa-hydro-1H-6,9-methano-pyrrolo[2,1-i][2,1]benzo-thia-zol-10-ol 5,5-dioxide.

In the title compound, C13H15NO3S, the sole classical hydrogen-bond donor is involved in an intramolecular O—H⋯N hydrogen bond. In the crystal structure, pairs of molecules related by inversion centres are linked by pairs of weak intermolecular C—H⋯O interactions; these centrosymmetric pairs are, in turn, linked further by weak intermolecular C—H⋯O interactions, forming two-dimensional sheets oriented parallel to (101).