The efficient simultaneous activation of cyclohexenones or simple alkyl acyclic enones and 2‐hydroxynitrostyrenes was realized by using a prolinol thioether catalyst. Thus, a highly chemo‐, diastereo‐ and enantioselective synthesis of functionalized tetrahydroxanthenones and chromanes with up to three contiguous stereocenters was developed.
Multifunctional 3‐amino‐4‐dialkylphosphono‐2‐quinolinones have been prepared by “one‐pot” nucleophilic addition and regioselective ring enlargement of imino isatins. The addition reaction between imino isatins and dialkyl (diazomethyl)phosphonate proceeds smoothly using potassium carbonate as a catalyst, and a subsequent regioselective ring expansion promotes by salicylic acid to afford the desired products in high yields.
A three‐component reaction of 3‐(tri‐n‐butylstannyl)allyl acetates, aldehydes, and triorganoboranes in the presence of a palladium‐Xantphos catalyst system predominately gave (E)‐anti‐homoallylic alcohols with high diastereoselectivity and good to high levels of alkene stereocontrol. An efficient chirality transfer was observed when an enantioenriched substrate was employed. The reaction was initiated by the formation of an allylic gem‐palladium/stannyl intermediate, which subsequently underwent allylation of the aldehyde by an allyltributyltin followed by a coupling reaction of the in‐situ‐generated (E)‐vinylpalladium acetate with the triorganoborane.
A novel method for the synthesis of 3‐iodoquinolines was developed by copper‐catalyzed tandem annulation from diaryliodoniums, nitriles, and 1‐iodoalkynes. It is a method that is characterized by the most convenient operation and wide molecular diversity.
A transition metal‐free and efficient method for the synthesis of 3‐alkynylpyrrole‐2‐carboxylates from diynones and glycine esters or 2‐aminoacetophenone hydrochloride has been developed. This transformation provides a large range of substituted pyrroles in good to excellent yields with the elimination of water as the only by‐product. The detailed mechanistic studies elucidated that this transformation involves a Michael addition/intramolecular cyclodehydration process.
A catalytic enantioselective synthesis of α‐arylaminocyclobutanones from racemic α‐hydroxycyclobutanone and a selection of N‐alkylanilines has been established, via a tandem condensation/keto‐enol tautomerization process reminiscent of the Amadori and Heyns rearrangements.
A practical and environmentally friendly strategy for generating alkoxycarbonyl radicals from readily available carbazates under metal‐free conditions has been developed. In the presence of tetrabutylammonium iodide and tert‐butyl hydroperoxide, 2‐isocyanobiphenyls smoothly underwent radical alkoxycarbonylation with carbazates to afford phenanthridine‐6‐carboxylates.
α‐Substituted β‐acetyl amides could undergo C C bond cleavage to form α‐keto amides when treated with copper(II) chloride (CuCl2) and boron trifluoride diethyl etherate (BF3⋅OEt2) under an oxygen atmosphere. The yield can be increased by the addition of tert‐butyl hydroperoxide which alone can also effect the reaction. The reaction provides a new protocol for the synthesis of α‐keto amides.
A 1:1 mixture of water‐polyethylene glycol (PEG) facilitated the 1,3‐dipolar cycloaddition of benzoylnitromethane/ethyl 2‐nitroacetate with terminal alkynes or alkenes leading to isoxazoles or isoxazolines under green conditions. The methodology is free from the use of any base, catalyst, dehydrating agent or hazardous solvent.
The transition metal‐catalyzed transfer of silicon nucleophiles onto various electrophiles has recently gained considerable attention, due to the now readily available silicon pro‐nucleophiles such as silylboronates. Our interest lies in the addition of such species to acid derivatives for the generation of acylsilanes. We report herein an efficient method to synthesize these compounds, starting from easy‐to‐form anhydrides, with very good yields.
A simple and efficient catalyst‐free method for isothiocyanatoalkylthiation of styrenes has been developed. The protocol uses (alkylthio)pyrrolidine‐2,5‐diones and trimethylsilyl isothiocyanate as the isothiocyanatoalkylthiolating reagents, dimethylformamide (DMF) as the solvent, and the reactions were completed within one hour with tolerance of some functional groups. No catalyst and additive were required in the reaction system, which avoided any contamination of transition metal catalysts in the target products. Therefore, the present method provides a convenient, efficient and practical strategy for the synthesis of compounds by a combination of sulfides and isothiocyanates.
The catalytic asymmetric [4+2] annulations of isatins with but‐3‐yn‐2‐one catalyzed by the Cinchona alkaloids‐derived oragnocatalyst (DHQD)2PHAL have been developed in the presence of 3.0 equivalents of D ‐diethyl tartrate in the mixed solvent (diphenyl ether/diethyl ether=1/1) or a slightly modified one, affording the corresponding substituted spiro[indoline‐3,2′‐pyran]‐2,4′(3′H)‐diones in good to excellent yields with high enantioselectivities under mild conditions.
Isoindolin‐1‐ones and isoquinolin‐1‐ones were selectively synthesized from the reaction of 2‐halobenzoic acid, arylalkynylcarboxylic acid and ammonium acetate (NH4OAc) in the presence of cesium carbonate (Cs2CO3) and a copper catalyst. Conducting the reaction under one‐pot conditions provided isoindolin‐1‐ones in good yields. Changing the addition sequence of ammonium acetate after all reagents had reacted at 120 °C for 6 h selectively produced isoquinolin‐1‐ones. A variety of arylalkynylcarboxylic acids produced the corresponding isoindolin‐1‐ones and isoquinolin‐1‐ones in good yields.
The combination of benzyl bromide, sodium hydroxide and 15‐crown‐5 in tetrahydrofuran is shown to be an efficient method for installing benzyl groups at both the 4‐ and 6‐positions regioselectively directly from peracetylated N‐trichloroacetyl‐protected glucosamine and galactosamine. Application of this benzylation strategy proved to significantly shorten the synthetic route to hyaluronic acid tetra‐ and hexamers.
