Non‐Enzymatic Oxidation of a Pentagalloylglucose Analogue into Members of the Ellagitannin Family

The occurrence of more than 1000 structurally diverse ellagitannins has been hypothesized to begin with the oxidation of penta‐O ‐galloyl‐β‐d ‐glucose (β‐PGG) for the coupling of the galloyl groups. However, the non‐enzymatic behavior of β‐PGG in the oxidation is unknown. Disclosed herein is which galloyl groups tended to couple and which axial chirality was predominant in the derived hexahydroxydiphenoyl groups when an analogue of β‐PGG was subjected to oxidation. The galloyl groups coupled in the following order: at the 4,6‐, 1,6‐, 1,2‐, 2,3‐, and 3,6‐positions with respective S ‐, S ‐, R ‐, S ‐, and R ‐axial chirality. Among them, the most preferred 4,6‐coupling reflected the what was observed for natural ellagitannins. A new finding was that the second best coupling occured at the 1,6‐positions. With the detection of a 3,6‐coupled product, this work demonstrated that even ellagitannin skeletons with an axial‐rich glucose core may be generated non‐enzymatically.     

Copper(I)‐Catalyzed Chemoselective Coupling of Cyclopropanols with Diazoesters: Ring‐Opening C−C Bond Formations

Reported herein is an exceptional chemoselective ring‐opening/C(sp³)−C(sp³) bond formation in the copper(I)‐catalyzed reaction of cyclopropanols with diazo esters. The conventional O−H insertion product is essentially suppressed by judicious choice of reaction conditions. DFT calculations provide insights into the reaction mechanism and the rationale for this unusual chemoselectivity.     

Intramolecular Benzoin Reaction Catalyzed by Benzaldehyde Lyase from Pseudomonas Fluorescens Biovar I

Intramolecular benzoin reactions catalyzed by benzaldehyde lyase from Pseudomonas fluorescens biovar I (BAL) are reported. The structure of the substrates envisaged for this reaction consists of two benzaldehyde derivatives linked by an alkyl chain. The structural requirements needed to achieve the intramolecular carbon–carbon bond reaction catalyzed by BAL were established. Thus, a linker consisting of a linear alkyl chain of three carbon atoms connected through ether‐type bonds to the 2 and 2′ positions of two benzaldehyde moieties, which could be substituted with either Cl, Br, or OCH₃ at either the 3 and 3′ or 5 and 5′ positions, were suitable substrates for BAL. Reactions with 61–84 % yields of the intramolecular product and ee values between 64 and 98 %, were achieved.     

Shaping Antiaromatic π‐Systems by Metalation: Synthesis of a Bowl‐Shaped Antiaromatic Palladium Norcorrole

The synthesis of a bowl‐shaped antiaromatic molecule was achieved through the deformation of a planar antiaromatic porphyrinic π‐conjugation system by insertion of palladium into the small cavity of a metal‐free norcorrole. The bowl‐to‐bowl inversion dynamics of the antiaromatic Pd‐coordinated norcorrole was determined by variable‐temperature ¹H NMR spectroscopy. The metal‐free norcorrole was prepared from acid‐induced demetalation of a copper norcorrole, which was obtained from the intramolecular coupling of a bis(diiododipyrrin) copper complex with copper thiophenecarboxylate.     

Synthesis of Polysubstituted Iodoarenes Enabled by Iterative Iodine‐Directed para and ortho C−H Functionalization

Among halogenated aromatics, iodoarenes are unique in their ability to produce the bench‐stable halogen(III) form. Earlier, such iodine(III) centers were shown to enable C?H functionalization ortho to iodine via halogen‐centered rearrangement. The broader implications of this phenomenon are explored by testing the extent of an unusual iodane‐directed para C?H benzylation, as well as by developing an efficient C?H coupling with sulfonyl‐substituted allylic silanes. Through the combination of the one‐shot nature of the coupling event and the iodine retention, multisubstituted arenes can be prepared by sequentially engaging up to three aromatic C?H sites. This type of iodine‐based iterative synthesis will serve as a tool for the formation of value‐added aromatic cores.     

Regiodivergent and Diastereoselective CuH‐Catalyzed Allylation of Imines with Terminal Allenes

A copper‐catalyzed, chemoselective hydrometalation process enables the use of simple allenes as allylmetal nucleophile surrogates in imine allylation reactions. By modulating the nitrogen‐protecting group, either highly branched‐ or linear‐selective addition can be achieved from the same allene. Both reactions exhibit excellent diastereoselectivity and broad functional‐group tolerance. Preliminary results indicate that good enantioselectivity can also be achieved in the linear‐selective reaction. Finally, a mechanistic model for the regiodivergence is proposed on the basis of density functional theory calculations.