Facile Synthetic Method and Crystal Structure of 2,3,3',4'-Biphenyltetracarboxylic Dianhydride

A facile method for the synthesis of 2,3,3＇,4＇-biphenyltetracarboxylic dianhydride（a-BPDA） was reported,which comprises the steps of the dehalogenative coupling of dimethyl 4-chlorophthalate（4-DMCP） and dimethyl 3-chlorophthalate（3-DMCP） catalyzed by low-cost（Ph 3 P） 2 NiCl 2,the hydrolysis of tetra-ester and the dehydration of tetra-acid.In contrast to the conventional methods,this method has the advantage of low cost,convenient manipulation,available condition,high purity and good overall yield.Moreover,the single crystal structure of a-BPDA was analyzed by X-ray diffraction method.The X-ray data suggest that a-BPDA is a rigid,non-coplanar and non-linear structure.It contains three crystallographically independent molecules,in which the dihedral angles of the two linked phenyl rings are 44.75（4）°,46.37（3）° and 42.32（3）°,respectively.The title molecule is governed by a stronger intermolecular interaction in contrast to van der Waals interaction because of the special positions of anhydride groups.

Highly enantio-stereoselective Ni-catalyzed reductive cyclization to cyclopentanes with chiral quaternary centres of trisubstituted allylic siloxanes

The construction of chiral quaternary carbon stereocenters is a significant challenge in asymmetric synthesis.Catalytic synthesis of these structures with trisubstituted allylic alcohols is highly important. However, most ofthe reported methodologies required noble transition-metals. Herein we reported the first highly asymmetricstereoselective synthesis of cyclopentanes bearing chiral quaternary carbon stereocenters of trisubstituted allylicsiloxanes by reductive cyclization of all carbon 1,6-alkynones with the non-noble nickel catalysis of Ni(cod)2 withP-chiral monophosphine ligand (S)-BIDIME. Various multi-substituted functionalized cyclopentanes were obtained in high yields (up to 96%), excellent enantioselectivities (up to >99% ee) and perfect stereoselectivities(>99:1 E/Z). Thirty-two examples were successfully established for this method. Clarified mechanism studieswere investigated first time by React-IR and DFT calculations to understand and explain the ligand-control ofexcellent enantio-stereoselectivity. Gram-scale reaction and control experiments were carried out. A new reactiondesign was proposed for further application of this type of catalysis.

Synthesis of Skipped Aminodienes by a Ni-Catalyzed Ring-Opening/Cross-Coupling Reaction of Vinylaziridines with Multifunctional Organoboronic Acids

Skipped dienes are of great importance but remain challenging to synthesize because of the presence of a sp hybrid carbon between the two alkenes.Herein,we have developed the first nickel-catalyzed regio-,(E)-stereo-and linear-selective ring-opening/cross-coupling reaction of vinylaziridines with organoboronic acids under mild conditions to construct various skipped aminodienes.The reaction exhibits wide functional-group compatibility,and could be adapted for the introduction of skipped aminodiene functionality into bioactive molecules.

Bioinspired Total Syntheses of Grayanotoxins II/III,Kalmanol,and Rhodomollacetals A–C with Three Distinct Skeletons

Grayanane diterpenoids,which have intricate molecular architecture and interesting pharmacological properties,have attracted considerable interest of organic chemists since 1970s.However,the total syntheses of grayanane diterpenoids have been accomplished by only seven groups,which have mainly focused on the same carbon skeleton.Herein,we disclose the bioinspired total syntheses of six grayanane diterpenoids with three distinct carbon skeletons:grayanotoxins II/III,kalmanol,and rhodomollacetals A–C.Among them,the total syntheses of rhodomollacetals A–C were achieved for the first time.The total syntheses feature a Ni-catalyzedα-vinylation ofβ-ketoester to construct a bicyclo[3.2.1]octane ring system,an intramolecular Pauson–Khand reaction of enyne to construct a 7/5-bicyclic ring system,a biomimetic 1,2-rearrangement of grayanane-type 5/7/6/5 skeleton to generate kalmane-type 5/8/5/5 skeleton,and a biomimetic oxidative cleavage of C2–C3 and C5–C6 bonds/skeletal reconstruction to construct a rhodomollacetal A skeleton.

Nickel-catalyzed reductive coupling reaction of monofluoroalkyl triflates with alkyl carboxylic acids toward the synthesis of α-alkyl-α-fluoro-alkylketones

The synthesis methods ofα-fluoro-arylketones were well-established through electrophilic/nucleophilic fluorination and transition metal catalyzed cross-coupling.However,due to the site selectivity and substrate restriction,only a few cases have been developed to affordα-alkyl-α-fluoro-alkylketones.Herein,we report a general and efficient method of preparing diverseα-alkyl-α-fluoro-alkylketones via nickelcatalyzed reductive coupling reaction of monofluoroalkyl triflates with low-cost industrial raw material alkyl carboxylic acids.These transformations demonstrate high efficiency,mild conditions,and excellent functional group compatibility.This strategy provides a general and efficient method for the synthesis ofα-alkyl-α-fluoro-alkylketones。