A novel metal‐free oxidative cross esterification of alcohols has been achieved using trichloroisocyanuric acid as an oxidant. The alcohols were converted in situ into their corresponding acyl chlorides, which were then reacted with primary and secondary aliphatic, benzylic and allylic alcohols and phenols. A wide variety of esters was obtained in satisfactory yields.
A metal‐free, tetraethylammonium bromide‐catalyzed oxidative coupling of aldehydes or alcohols with thiophenols or disulfides has been developed. This protocol affords an efficient and inexpensive approach to the synthesis of a wide range of thioesters in high yields.
The iron(III) chloride‐multicatalyzed dioxygenation of enamides with TEMPO in the presence of alcohols has been developed. This multicomponent domino process affords efficient new strategies for the synthesis of α‐oxy‐N‐acylhemiaminals or α‐oxyimides in good to excellent yields under mild conditions.
A simple and efficient domino protocol has been developed for the preparation of biologically important benzamides, 2,2‐diazidobenzofuran‐3(2H)‐ones and benzoxazolones from various structurally and electronically divergent acetophenones and ortho‐hydroxyacetophenones in the presence of molecular iodine, sodium azide and sodium bicarbonate at 100 °C in good to excellent yields.
A metal‐free vinylic carbon‐hydrogen bond thiolation has been developed. Under the catalysis of iodine (10 mol%), the cyclization of α‐alkenoyl ketene dithioacetals afforded a broad range of polyfunctionalized 2‐methylene‐3‐thiophenones in good selectivity with moderate to excellent yields via tandem iodocyclization and dehydroiodination. The synthetic strategy can also be extended to the cyclization of ortho‐methylthiophenyl vinyl ketones leading to 2‐methylene‐3‐benzothiophenones.
The reductive benzylation of aromatic and aliphatic aldehydes with benzylic halides is reported using a nickel/zinc catalyst system. In addition to benzylic halides, the first report on the addition of benzylic triflates, acetates, tosylates and tritylates to aldehydes is also presented. By this new method a range of alcohols was synthesized efficiently from aldehydes and benzylic substrates at room temperature in moderate to high yields. The mild reaction conditions and good functional group tolerance make this nickel‐catalyzed process synthetically useful for the synthesis of diverse benzylic alcohols.
A unique one‐pot synthesis of cyclic cis‐1,2‐amino alcohols from trans‐1,2‐azido alcohol precursors was developed. The key step is highlighted by the stereoselective reduction of the cyclic α‐alkoxy imines, which could be prepared from the corresponding azides by ruthenium catalysis under photolytic conditions. Remarkably, this unprecedented reaction pathway offers a stereodivergent access to structurally diverse cyclic 1,2‐amino alcohols.
In the presence of sodium carbonate, the [4+3] cycloadditions of α‐halogeno hydrazones with nitrones were performed efficiently, and affording 2,3,4,7‐tetrahydro‐1,2,4,5‐oxatriazepines in moderate to high yields.
A method for copper‐catalyzed aryltrifluoromethylation of N‐phenylcinnamamides is reported. This method provides a straightforward route to a variety of CF3‐containing 3,4‐dihydroquinolin‐2(1 H)‐ones with excellent regioselectivity and diastereoselectivity.
The palladium‐catalyzed oxidative Heck‐type allylation of β,β‐disubstituted enones, i.e., α‐oxoketene dithioacetals, was efficiently realized with allyl carbonates, providing a concise route to highly functionalized dienes. The present synthetic methodology utilizes the substrate activation strategy to activate the C H bond of β,β‐disubstituted enones by introduction of a 1,2‐dithiolane functionality to make the enone substrate highly polarized and thus increase its reactivity, demonstrating rare examples for transition metal‐catalyzed allylic substitution of ß,ß‐disubstituted enones through a Heck‐type allylation process.
An efficient copper‐catalyzed α‐aminoxylation of ketones with 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) is presented for the synthesis of 2‐aryloxy‐1‐aryl‐2‐(2,2,6,6‐tetramethylpiperidin‐1‐yloxy)ethanones in moderate to excellent yields. It is noteworthy that the copper/iron (Cu/Fe) catalyst can be recovered and reused several times with high catalytic reactivity.
We present the first organocatalytic asymmetric vinylogous Michael/cyclization reaction of α,α‐dicyanoalkenes with 3‐alkylideneoxindoles. A series of diversely structured spiro‐oxindole skeletons was smoothly delivered with excellent yields and stereoselectivity control (94–99% yields, >20:1 dr and 91 to >99% ee).
An asymmetric tandem Michael addition–lactonization between ortho‐nitrovinylphenols and azalactones was investigated for constructing 3,4‐dihydrocoumarin backbones with a quaternary amino acid moiety. Under the catalysis of the chiral squaramide derived from L ‐tert‐leucine, a wide range of substituted (E)‐2‐(2‐nitrovinyl)phenols and azalactones were well tolerated in this tandem reaction to provide the corresponding biologically significant 3,4‐dihydrocoumarin derivatives in excellent yields with high levels of diastereo‐ and enantioselectivity.
2,2‐Difluoro‐1,3‐diketones are introduced as gem‐difluoroenolate precursors for the first example of an organocatalytic asymmetric aldol addition with N‐benzylisatins to form 3‐difluoroalkyl‐3‐hydroxyoxindoles.
A straightforward approach for the chemodivergent synthesis of quinolines is described through site‐selective coupling of ortho‐aminoaryl ketones with α‐enolic dithioesters (DTEs) under solvent‐free conditions. The operationally and user‐simple one‐pot methodology is based on the trifunctional nature of DTEs. Both the carbonyl and the thiocarbonyl moiety in α‐enolic dithioesters were employed for the efficient construction of three differently substituted quinolines in a chemoselective manner simply by variation of an easy to handle acid catalyst.
A quinine‐derived thiourea catalysed the enantioselective addition of 4‐substituted pyrazolones to isatin‐derived ketimines, providing a variety of aminooxindole‐pyrazolone adducts containing congested vicinal tetrasubstituted stereocentres with excellent outcomes (up to 98% yield, >20:1 dr and 98% ee).
