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.
A new palladium‐catalyzed route to 3‐hydroxy‐4‐arylcyclopentanones and 4‐arylcyclopentenones in a diastereo‐ and enantioselective manner by a Heck–Matsuda desymmetrization was achieved from the commercially available meso cis‐4‐cyclopentene‐1,3‐diol. This method is highly practical, mild, high yielding and is carried out under “open vessel” conditions. Protected and unprotected substrates provide distinct products bearing considerable value as synthetic scaffolds for the synthesis of natural and unnatural bioactive compounds containing a five‐membered ring.
A series of 1,2‐ and 1,4‐dihydroquinolines has been successfully prepared. The Pd‐catalyzed intramolecular N‐arylation of Z‐enamines, formally prepared by the Horner–Wadsworth–Emmons olefination, proceeded efficiently to furnish the cyclized products. Depending on the cyclization conditions, substituted 1,4‐dihydroquinolines and further isomerized 1,2‐dihydroquinolines were independently obtained in high yields with an excellent control of isomerization of the double bond.
A method to prepare highly enantioenriched azaflavanones using an organocatalytic 6‐endo aza‐Michael addition has been described. A variety of 2‐aryl‐, 2‐vinyl‐ and 2‐methylazaflavanones were prepared in good yields (53–84%) and excellent enantioselectivities (97.6:2.4 to 99.3:0.7 er).
Iridium(III) and rhodium(III) complexes can catalyze the carbocyclization between 2‐phenylimidazo[1,2‐a]pyridine and α‐diazo esters. The reaction occurs via C H activation and dialkylation of the arene followed by intramolecular nucleophilic substitution. Iridium(III) and rhodium(III) catalysis offer complementary scopes with respect to the α‐diazo esters.
A highly efficient, iridium‐catalyzed, enantioselective hydrogenation of β,β‐disubstituted nitroalkenes has been developed. Using a complex consisting of iridium and (S,S)‐f‐spiroPhos as the catalyst, a variety of β,β‐disubstituted nitroalkenes were successfully hydrogenated to the corresponding chiral nitroalkanes with excellent enantioselectivities (up to 98% ee) and high turnover numbers (TON=1000).
A phosphane‐catalyzed [3+3] annulation of azomethine imines with ynones has been developed. Under mild reaction conditions, the reaction proceeds smoothly to afford tricyclic dinitrogen‐fused heterocyclic compounds in moderate to excellent yields with moderate to excellent stereoselectivies. Using a chiral phosphine as the catalyst, the reaction could work to give the cycloadduct in moderate yield with moderate enantioselectivity.
The asymmetric organocatalytic transfer hydrogenation of β‐acylamino and β‐tert‐butyloxycarbonylamino nitroolefins has been successfully realised in excellent enantioselectivities and yields (up to >99% ee, 97% yield) with a simple thiourea catalyst and a Hantzsch ester as hydrogen source, giving a direct access to enantiomerically pure β‐amino nitroalkanes.
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.
Through an unexpected CC bond migration, 2(E)‐enals were efficiently prepared highly stereoselectively in moderate to good yields via the sodium iodide/tert‐butyl(dimethyl)silyl chloride (NaI/TBSCl)‐mediated reaction of the easily available 2,3‐allenols. Based on a careful mechanistic study, including control experiments and deuterium‐labeling experiments, an electron‐withdrawing substituent group in the 4 position has been proven to be crucial and a possible mechanism has been proposed.
We report a triple vinylogous cascade reaction, yielding valuable spiro‐oxindolic cyclohexane derivatives. The three‐component domino process proceeds by way of a catalyzed Michael/1,6‐addition/vinylogous aldol sequence affording the products with six stereogenic centers and very high control over the stereochemistry. The chemistry is based on a rare example of asymmetric 1,6‐addition to linear 2,4‐dienals proceeding with complete δ‐site selectivity. Key to the reaction development was a directing group positioned at the β‐dienal position, which was essential for achieving highly predictable reaction outcomes.
A divergent synthesis of cyclitol derivatives has been developed utilizing an N‐heterocyclic carbene‐catalyzed benzoin‐type cyclization of C2‐symmetrical dialdoses. The resulting inososes are versatile intermediates, which are readily converted into not only inositols but also amino‐, deoxy‐, O‐methyl‐ and C‐methyl‐inositols.
A novel asymmetric [4+2] annulation of vinyl ketones with oxindole‐derived α,β‐unsaturated imines has been developed in the presence of a multifunctional thiourea‐phosphine catalyst derived from a natural amino acid, providing the first phosphine‐catalyzed enantioselective synthesis of 2′,3′‐dihydro‐1′H‐spiro[indoline‐3,4′‐pyridin]‐2‐ones in good yields with excellent stereoselectivities under mild conditions.
A visible‐light induced radical reaction of vinyl azides and α‐carbonyl benzyl bromides was developed, which provides an efficient route to polysubstituted quinolines via a C C and C N bond formation sequence.
