A boryl-migratory semipinacol rearrangement

The semipinacol rearrangement is one of the classic yet useful synthetic tools in organic synthesis. However, semipinacol rearrangements involving heteroatom-migration are rare. Reported herein is a boryl-migratory semipinacol rearrangement of α-hydroxyallylboronates and α-hydroxypropargylboronates triggered by diverse halogen-, oxygen-, sulfur-and seleniumcontaining electrophiles. The protocol leads to a mild and facile access to organoborons bearing valuable functionalities. The σ(C–B) hyperco...     

Synthesis of benzodiquinanes via tandem palladium-catalyzed semipinacol rearrangement and direct arylation

A palladium-catalyzed tandem semipinacol rearrangement/direct arylation reaction using α-aryl isopropenyl-tert-cyclobutanols has been developed. This reaction gives access to benzodiquinanes in moderate to good yields and tolerates alkyl-, alkoxy-, and halogen-substituted aryl groups.     

Tandem Lewis acid catalyzed coupling/semipinacol rearrangement of allylic alcohol

Construction of the polyaryl quaternary unit through a ZnBr2 catalyzed tandem coupling/semipinacol rearrangement participated by allylic cations was reported for the first time.     

Formal synthesis of actinoranone using a one-pot semipinacol rearrangement/Wittig reaction

Here, we report a formal synthesis of the marine cytotoxic meroterpenoid actinoranone. Key steps include a semipinacol rearrangement/Wittig reaction sequence and a chiral pool approach for the syntheses of the tetralone and the ocatalin fragments, respectively. The presented route provides access to the natural product in 14 steps in the longest linear sequence.     

Recent applications of organocatalysts in asymmetric aldol reactions

The asymmetric aldol reaction is one of the most powerful synthetic tools for carbon–carbon bond-forming reactions. This method provides a beneficial route to access chiral β-hydroxy carbonyl compounds, which are versatile synthetic motifs found in biologically active natural products and pharmaceutically attractive intermediates. The aim of this review is to provide an overview of the many contributions and recent advances in the field of organocatalytic asymmetric aldol reactions.     

Photo-induced phosphorus radical involved semipinacol rearrangement reaction:Highly synthesis ofγ-oxo-phosphonates

Hydroxyphosphoric acids display the unique biological activities,and they have some attractive prospects as clinical drug moleculars.Herein,a new approach for the synthesis ofγ-oxo-phosphonates(the precursor of hydroxyphosphoric acid)has been established through the semipinacol rearrangement tactic involved the photo-induced phosphorus radical process.Most important,this transformation is avoid of the external oxidants,and occurs very well under the sunlight irradiation,meanwhile theγ-oxo-phosphonate was easily derivatized to obtainγ-hydroxyphosphoric acid,thus highlights the synthesis value of this method.     

Recent development of vinylogous Mukaiyama aldol reactions

The vinylogous Mukaiyama aldol reaction (VMAR) is a powerful tool of polyketide synthesis, which constructs a large size structure by simultaneous introduction of the stereogenic center(s) and the α,β-unsaturated carbonyl group. A variety of stereocontrolled VMARs have been developed and applied to natural product synthesis. This review is focused on recent development of the vinylogous Mukaiyama aldol reaction using s-trans silyl dienolates.     

Recent developments and applications of EMMA in enzymatic and derivatization reactions

This review provides systematic coverage of examples in the field of in-capillary electrophorecially mediated microanalysis (EMMA). The recent developments and applications in the time period up to mid 2011 have been described, as well as relevant older papers. The basic principles and modes of in-capillary assays have been demonstrated. An overview is also given of the various injection, separation and detection modes implemented in combination with EMMA. The review is presented in two parts mainly dealing with (i) enzymatic and (ii) derivatization or chemical reactions. Finally, the future trends of CE in performing and monitoring reactions have been drawn.     

Axially chiral dicarboxylic acid catalyzed asymmetric semipinacol rearrangement of cyclic β-hydroxy-α-diazo esters

The development of axially chiral dicarboxylic acid catalyzed desymmetrizing asymmetric semipinacol rearrangement of symmetrically substituted six-membered cyclic β-hydroxy-α-diazo esters is reported as a means to give chiral cycloheptanones with good enantioselectivities.     

Arylation and vinylation of alkenes based on unusual sequential semipinacol rearrangement/Grob fragmentation of allylic alcohols

Alkenes can be stereoselectively arylated and vinylated without transition-metal catalyst under mild conditions through an interesting NBS-promoted semipinacol rearrangement and a subsequent unusual NaOH-mediated Grob fragmentation.     

Stereochemistry and rearrangement reactions of hydroxylignanolactones

Various conflicting data on the rearrangement and absolute stereochemistry of hydroxylignano-9,7'-lactones are resolved using 18O labeled compounds, also confirmed by an X-ray analysis of a pure lignano-9,7'-lactone enantiomer, obtained for the first time. Under NaH/DMF rearrangement conditions a silyl protected hydroxylignano-9,9'-lactone underwent an unexpected silyl migration.     

Progressive studies on the novel samarium-catalyzed diastereoselective tandem semipinacol rearrangement/Tishchenko reduction of secondary alpha-hydroxy epoxides

A novel and highly diastereoselective samarium-catalyzed tandem rearrangement/reduction of secondary alpha-hydroxy epoxides, which involves a C1 to C3 carbon migration rearrangement and a very interesting hetero-Tishchenko reduction of the intermediate aldehyde and the reductant aldehyde, has been reported. This reaction could be developed to provide a facile and stereoselective construction of 2-quarternary 1,3-diol units with an hydroxymethyl moiety attached to the diastereogenic quaternary carbon center. Detailed investigations have been carried out concerning the screening of the aldehydes as a reductant, the optimization of reaction conditions, and the substrate scope of this tandem reaction. A catalytic cycle for this reaction, the electronic and steric effects of the reductant aldehydes, and the mechanism for the acyl migration of 1,3-diol monoesters are proposed.     

Photocatalytic aerobic oxidation/semipinacol rearrangement sequence: a concise route to the core of pseudoindoxyl alkaloids

A visible light-induced photocatalytic aerobic oxidation/semipinacol rearrangement has been successfully developed. This methodology allows for efficient conversion of a wide range of indoles into the synthetically significant 2,2-disubstituted indolin-3-ones, the core structure of pseudoindoxyl alkaloids, under mild reaction conditions.     

Recent applications of gold-catalyzed cascade reactions in total synthesis of natural product

From the point of the view of the synthetic efficiency, the concept ‘step economy’ was required in total synthesis of natural product. Recently, versatile gold-catalyzed cascade reactions have been developed, and relating reports on practical applications in total synthesis has increased. This digest focuses and summarizes the gold-catalyzed reaction cascades in natural product synthesis during last five years with brief discussion on the reaction mechanism of the key gold-catalyzed cascade transformations.     

Recent progress on catalytic [1,3]-oxygen rearrangement reactions from nitrogen to carbon atoms

[1,3]-Rearrangement reactions of an oxygen atom from a nitrogen atom to a carbon atom is an ideal way to synthesize highly elaborate molecules in which nitrogen and oxygen functionalities are vicinally arranged. Recently, it has been disclosed that this intriguing transformation takes place in the presence of Lewis acidic metal catalysts. In this digest, we summarize recent findings on the catalytic [1,3]-oxygen rearrangement reactions, such as direct [1,3]-rearrangement of N-oxygenated enamines and anilines, as well as π-acidic metal-catalyzed cascade reaction involving the [1,3]-rearrangement process.