STEREOCHEMISTRY OF THE BENZILIC ACID-TYPE REARRANGEMENT IN BASE-CATALYZED AUTOXIDATION OF 3α,5-CYCLO-5α-CHOLESTANE-6-ONE

The configuration of the hydroxy acid 2, a product from base-catalyzed autoxidation of 3α,5-cyclo-5α-cholestane-6-one,was established on the basis of NMR techniques and the mechanism of the formation of 2 was discussed.

Production of Bio-Phenols for Industrial Application:Scale-Up of the Base-Catalyzed Depolymerization of Lignin

Objective of this study was the investigation on the up-scaling of base-catalyzed depolymerization (BCD) of lignin to pilot plant dimension. The cleavage process was carried out in dilute alkaline solution at temperatures up to 340°C and a pressure of 25 MPa in a continuously operated tubular flow reactor with throughputs up to 20 kg/h. Investigations included the proof of the feasibility of the scale-up as well as a parameter study on the cleavage of hardwood Organosolv lignin and softwood Kraft lignin within the established pilot plant. Yields and molecular compositions of the isolated product fractions BCD-oil (liquid phenolic fraction) and BCD-oligomers (solid phenolic fraction) are similar to those described in technical lab scale, showing a good scalability. Here, BCD-oils rich in phenolic monomers such as guaiacol, catechol and/or syringol were obtained with a content of up to 13.3 wt% and 14.5 wt% from Organosolv lignin and Kraft lignin, respectively. Formation of BCD-oligomers strongly depends on temperature and residence times within the reactor.

Base-catalyzed diborylation of alkynes: synthesis and applications of cis-1,2-bis(boryl)alkenes

An efficient, transition-metal free, and practical approach to cis-bis(boryl)alkenes from various alkynes was disclosed in the presence of a catalytic amount of K_2CO_3 under mild conditions. Meanwhile, tetrasubstituted alkenes and phenanthrene derivatives were readily constructed from the target diborylalkenes via Suzuki-Miyaura cross coupling.

New preparation method for halogenated ethanes and methanes via base-catalyzed halogen dance

Although literature abounds with examples of formation of perhaloalkanes by photo-lytic or Lewis-acid induced halogen exchange reactions involving radical or carbocationintermediates,the procedures are seldom applicable to the preparation of perhaloalkanes ingood yields under mild conditions.Recently,we have reported the spontaneous reactionsof some perhalofluoroalkanes with various types of nucleophiles.All these reactions areinitiated by the halophilic attack of nucleophiles on C—Br or C—Cl bonds,followed byanionic chain steps involving carbanion as well as olefin intermediates.Notably,the latter areformed after the β-elimination of a good leaving group from the former.On the other hand,it is well known that halogenated carbanions can effectively make halophilic attacks on theC—X bonds of other halogenated substrates,e.g.,in the“halogen dance”of Bunnett.There-

A facile one-pot synthesis of new thieno-[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives

A facile one-pot synthesis of new 3-arylthieno[2,3-d]pyrimidine-2,4（1H,3H）-diones via base-catalyzed cyclocondensation of ethyl 2-amino-4,5-dimethylthiophene-3-carboxylate with aryl isocyanates is described.

Recent advances in polyoxoniobate-catalyzed reactions

The search for polyoxometalate-based catalysts has long attracted interest.Being designable in structure,stable and effective,polyoxoniobate-based catalysts have an exciting prospect for industrial applications.This paper not only summarizes recent advances in classic polyoxoniobate-catalyzed reactions,including chemical warfare agents and organic dyes degradation,epoxidation reactions,photocatalytic hydrogen evolution and base-catalyzed reactions but also discusses some representative cases and the speculative mechanism related to structures.In addition,the current challenges and perspectives in the fabrication of more efficient and promising polyoxoniobate-based catalysts are also presented.

Synthesis of anti-vicinal diboronates from diarylethynes and B2pin2

Anti-vicinal diboronates were fabricated from easily available diarylethynes and B2pin2via a basecatalyzed domino-borylation-protodeboronation(DBP)strategy under transition-metal-free conditions.Under the standard conditions,reactants with a range of different classes of functional groups on the rings,such as Me O,Me S,CF3O,Me2N,TMS,I,Br,Cl,F,and the thiophene ring,were tolerated.Downstream transformation of the vicinal diboronates provided a facile pathway for obtaining vicinal diols by mild oxidation with Na BO3,and a new deuteriation technique was developed in order to acquire1,2-diarylethanes-1,2-d2and 1,2-diarylethanes-1,1,2,2-d4.The new deuteriation strategy developed in this study may provide a new research direction for deuteriation chemistry.