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.
Copper chloride‐catalyzed aerobic oxidative annulation of N‐furfuryl‐β‐enaminones provides access to polysubstituted pyrroles and indoles. This protocol involves an unprecedented copper chloride‐catalyzed oxidative chlorination of furan and pyrrole rings with oxygen as the terminal oxidant.
A general method for the N‐alkylation of NH‐sulfoximines and NH‐sulfondiimines has been developed, employing alkyl bromides with KOH in DMSO at room temperature. A variety of previously inaccessible N‐alkylated sulfoximines and sulfondiimines was prepared in good to excellent yields (up to 97%). As an application, the conditions were used to access the biologically active Suloxifen.
A general method to generate umpolung of aldimines with cyanide was developed via the addition of cyanide to aldimines followed by a proton transfer from the carbon atom to the nitrogen atom in the resulting cyanide adducts. This novel method was successfully applied to the first imino‐Stetter reaction of aldimines obtained from 2‐aminocinnamic acid derivatives and aromatic aldehydes with cyanide, affording 2‐aryl‐substituted indole‐3‐acetic acid derivatives. Furthermore, the usefulness of this method was successfully demonstrated by the synthesis of an FPTase inhibitor, one of the biologically important 2‐arylindole‐3‐acetic acid derivatives.
An efficient and concise one‐pot strategy for the direct alkylation of quinoline N‐oxides via palladium‐catalyzed dual C H bonds activation has been developed. This methodology provides quinoline‐containing heterocyclic molecules in moderate to excellent yields.
A sequential one‐pot synthesis of Michael adducts of aroylmethylidenemalonates with activated aromatics is described. The method involves treatment of trans‐2‐aryl‐3‐nitro‐cyclopropane‐1,1‐dicarboxylates with boron trifluoride etherate to form aroylmethylidenemalonates in situ and then addition of activated aromatics such as indoles, carbazole, pyrrole, thiophenes, methoxybenzenes and benzodioxole followed by a catalytic amount of indium(III) triflate to the same reaction vessel. To prove the synthetic potential of the resulting Michael adducts, one of the adducts was transformed into a pharmaceutically interesting dihydropyridazinone derivative.
An enantioselective organocatalytic addition of nitroalkanes to oxindolylideneindolenines in the presence of bifunctional organocatalysts has been established to provide an efficient entry to 3,3‐disubstituted oxindole derivatives in high yields and with excellent enantioselectivities. The transformation has been applied to the preparation of the key intermediate for a formal total synthesis of (+)‐gliocladin C.
Zinc‐catalyzed 1,4‐oxofluorinations of 3‐en‐1‐ynamides with Selectfluor in acetonitrile/water proceeded with high regio‐ and stereoselectivity, giving E‐configured γ‐fluoro‐α,β‐unsaturated amides efficiently. Our control experiments indicate that kinetically unstable C‐bound zinc dienolates are chemically reactive to undergo SE2′‐electrophilic fluorinations whereas the detectable O‐bound dienolates preferably undergo protodemetalation reactions instead.
A general and efficient method for the synthesis of oxazolidin‐2‐ones and imidazolidin‐2‐ones directly from 1,3‐diols and 3‐amino alcohols has been developed using the same reagent combination of iodobenzene dichloride (PhICl2) and sodium azide (NaN3).
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.
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 Brønsted acid, trifluoromethanesulfonimide [HN(SO2CF3)2], was found to catalyze reductive β‐alkylation of pyrroles with carbonyl compounds and hydrosilanes. This metal‐free process features lower catalyst loadings compared to the original indium variant and exclusive generation of β‐alkylpyrroles.
