A new catalytic difluorohydration of β-alkynyl ketones using NFSI as the fluorinating reagent has been established, diastereoselectively furnishing a range of structurally diverse difluoride 1,5-dicarbonyl products through C(sp3)–H fluorination. Notably, the sterically encumbered t-butyl functionality located at the α-position of the carbonyl group of substrates 1 showed excellent diastereoselectivity (up to >99 : 1 dr). The reaction enabled multiple bond-forming events including two C(sp3)–F formation through Ag-catalysis to provide a highly efficient and practical method toward difluoride 1,5-dicarbonyls, some of which were successfully converted into difluorinated isoquinolines.

A new cascade three-component halosulfonylation of 1,7-enynes for efficient synthesis of densely functionalized 3,4-dihydroquinolin-2(1H)-ones has been established from readily accessible arylsulfonyl hydrazides and NIS (or NBS). The reaction pathway involves in situ-generated sulfonyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in continuous multiple bond-forming events including C–S, C–C and C–I (or C–Br) bonds to rapidly build up molecular complexity.

•A metal-free desulfonylation of N-aryl-N-arylsulfonyl-acrylamides is developed.•The mechanism involves 5-exo-trig cyclization, desulfonylation, and aryl migration.•This method installs C–S and C–C bonds with cleavage of N–S and C–S bonds.A metal-free arylsulfonyl radical-triggered desulfonylation of N-aryl-N-arylsulfonyl-acrylamides under mild conditions for the facile synthesis of a series of sulfonylated amides has been described. The radical transformation simultaneously installs C–S and C–C bonds with concomitant cleavage of N–S and C–S bonds through continuous 5-exo-trig cyclization, desulfonylation, and aryl migration sequence.

A new metal-free bicyclization reaction of 1,7-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using tert-butyl hydroperoxide and tetrabutylammonium iodide. The reactions occurred through sulfonylation/6-exo-dig/6-exo-trig bicyclization/in situ desulfonylation/5-exo-trig cyclization/alkyl or alkenyl migration cascade mechanism to give benzo[j]phenanthridines regioselectively.

A metal-free synthesis of bifunctionalized indole derivatives was developed through a novel TBHP/TBAI-mediated oxidative coupling of C2,C3-unsubstituted indoles with arylsulfonyl hydrazide. Under the same conditions C3-methyl substituted indoles underwent a diazotization process, affording 2-sulfonyldiazenyl-1H-indoles. The former reaction simultaneously established C–S and C–N bonds through selective sulfonylation and diazotization of the indole framework, enabling a mild and practical access to polyfunctionalized indoles with good to excellent yields.

•Combined mechanical-chemical pretreatment for wheat straw was designed.•Pretreated straws with great lignin removal and structure disruption were obtained.•Process analysis of pretreatment was conducted to determined significant factors.•4-fold enhanced saccharification yield (∼92%) was achieved from pretreated straws.•Lignin could be partially recovered and collected from straw via pretreatment.Lignocelluloses featuring complicated structure and poor degradability usually require pretreatment before its utilization. In this study, an ultrasonic-assisted pretreatment by using quaternary ammonium hydroxide was introduced to enhance biodegradability of lignocellulosic biomass. The synergistic chemical and mechanical pretreatment were supposed to be responsible for both external surface destruction and internal structure disruption of lignocelluloses. High-efficient lignin removal accompanied with obvious structural (crystallinity) transformation was achieved in the pretreated straws. Process analysis indicated that factors of time, temperature, concentration of solvent, and ultrasound power intensity turned out to be significant for pretreatment, and a 4-fold increased saccharification yield of around 92.4% as compared to untreated straw was obtained from the wheat straw pretreated by 15% solvent at 50 °C for 0.5 h in power intensity 344 W/cm2. All results suggest that the combined chemical and mechanical treatment can significantly improve the bio-accessibility of lignocelluloses, leading to the enhanced utilization efficiency.Download high-res image (114KB)Download full-size image

•Cellobiose is a zero-calorie sweetener and dietary fiber.•Value-added cellobiose was synthesized from sucrose by an enzyme cocktail.•A kinetic model was developed for data accommodation and process optimization.•Use of thermophilic enzymes at elevated temperatures increases reaction rate.Cellobiose is a zero-calorie functional sweetener and a potential healthy food/feed additive. Current production methods of cellobiose from high-purity cellulose always suffer from low product yields and high separation costs. Here one-pot biotransformation composed of three thermophilic enzymes sucrose phosphorylase (SP) from Thermoanaerobacterium thermosaccharolyticum, glucose isomerase (GI) from Streptomyces murinus, and cellobiose phosphorylase (CBP) from Clostridium thermocellum was designed to convert sucrose to cellobiose. To reveal the underlying relationship within the three enzymes and optimize reaction conditions, a kinetic model was developed. Model simulation predicted the optimal SP:GI:CBP enzyme loading ratio in terms of enzyme unit was 0.5:1.0:1.5. The enzyme cocktail with the optimal ratio converted 100 mM sucrose to 62.3 mM cellobiose within 10 h. Model simulation also found out that the optimal phosphate concentration was approximately 10.3 mM for 100 mM sucrose, which was validated by experimental data. This study could assist the sugar industry to diversify the production of new value-added products from sucrose.Download high-res image (103KB)Download full-size image

A new cascade three-component halosulfonylation of 1,7-enynes for efficient synthesis of densely functionalized 3,4-dihydroquinolin-2(1H)-ones has been established from readily accessible arylsulfonyl hydrazides and NIS (or NBS). The reaction pathway involves in situ-generated sulfonyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in continuous multiple bond-forming events including C–S, C–C and C–I (or C–Br) bonds to rapidly build up molecular complexity.

A new catalytic difluorohydration of β-alkynyl ketones using NFSI as the fluorinating reagent has been established, diastereoselectively furnishing a range of structurally diverse difluoride 1,5-dicarbonyl products through C(sp3)–H fluorination. Notably, the sterically encumbered t-butyl functionality located at the α-position of the carbonyl group of substrates 1 showed excellent diastereoselectivity (up to >99:1 dr). The reaction enabled multiple bond-forming events including two C(sp3)–F formation through Ag-catalysis to provide a highly efficient and practical method toward difluoride 1,5-dicarbonyls, some of which were successfully converted into difluorinated isoquinolines.

A metal-free synthesis of bifunctionalized indole derivatives was developed through a novel TBHP/TBAI-mediated oxidative coupling of C2,C3-unsubstituted indoles with arylsulfonyl hydrazide. Under the same conditions C3-methyl substituted indoles underwent a diazotization process, affording 2-sulfonyldiazenyl-1H-indoles. The former reaction simultaneously established C–S and C–N bonds through selective sulfonylation and diazotization of the indole framework, enabling a mild and practical access to polyfunctionalized indoles with good to excellent yields.

A new metal-free oxidative hydrophosphinylation of 1,7-enynes for forming polyfunctionalized 3,4-dihydroquinolin-2(1H)-ones has been realized using readily accessible diarylphosphine oxide and TBPB as an oxidant. The reaction pathway involves an in situ-generated P-centered radical-triggered α,β-conjugate addition/6-exo-dig cyclization/H-abstraction sequence, providing a direct and promising protocol for the formation of C–P, C–C and C–H bonds and rapid construction of complex heterocyclic compounds.