A simple hydrido‐cobalt complex efficiently catalyses the highly regio‐ and stereoselective dimerisation of various terminal arylacetylenes under mild conditions. The corresponding (E)‐1,4‐enynes are obtained as sole isomers with good to excellent yields. DFT calculations revealed that the reaction proceeds via a C H activation/hydrocobaltation pathway.
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.
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 mild and efficient transition metal‐free approach has been developed for the synthesis of highly substituted chiral morpholines from alkenols by amino acid‐derived iodine(III) reagents via a 6‐exo‐trig cyclization. The key features of this work include the formation of three chiral centers with a high diastereomeric ratio, broad functional group compatibility, and atom/time economic methodology.
We have developed an electrophilic addition of allylic carbocations to 2‐cyclopropylidene‐2‐arylethanols constructing carbon‐carbon bonds with excellent regio‐ and stereoselectivities. The reaction affords 3‐oxabicyclo[3.2.0]heptanes in moderate to good yields via the electrophilic addition/ring‐opening/vinyl group shift/intramolecular cyclization sequence.
In this study, enantiopure imidazolidinones containing two hydroxyphenyl groups were synthesized, and the Williamson synthesis of the chiral bisphenols thus prepared with dihalides afforded polyethers containing chiral imidazolidinone repeating units. These chiral imidazolidinone polyethers exhibited excellent catalytic activity in the asymmetric Diels–Alder reaction. With the use of these polymeric catalysts, enantioselectivities up to 99% were obtained, higher than those obtained by the corresponding monomeric imidazolidinone catalyst in homogeneous solution. The polymeric catalysts were found to be insoluble in commonly used organic solvents, and they could be repeatedly used without the loss of activity.
Vinyl nosylates derived from 1,3‐dicarbonyl compounds could be engaged in Suzuki–Myaura cross coupling reactions with aryl‐, vinyl‐ and methylboronic acids or trifluoborate derivatives at room temperature in the presence of 2 mol% of [1,1′‐bis(diphenylphosphino)ferrocene]dichloropalladium(II) [PdCl2(dppf)]. One‐pot procedures have been set up for practical and efficient nosylation–cross‐coupling reactions. Nosylate, as a cheap novel pseudo‐halide, gives very stable compounds and is very efficient in Suzuki–Myaura cross coupling reactions (21 examples, 44–99%).
The reactivity of pyrrole derivatives for palladium‐catalysed desulfitative arylation has been investigated. 1‐Methyl‐, 1‐phenyl‐ and 1‐benzylpyrroles were successfully coupled with a variety of benzenesulfonyl chlorides using a phosphine‐free catalyst. Highly regioselective arylations at carbon C2 of pyrroles were observed in all cases. A wide variety of substituents on the benzenesulfonyl derivative was tolerated. It should be noted that even bromo‐ and iodo‐benzenesulfonyl chlorides were successfully coupled with pyrrole derivatives without cleavage of the C Br or C I bonds, allowing further transformations. Surprisingly, with indoles, mixtures of C2‐ and C3‐arylation products were obtained.
By applying carbonyl compounds as sources of alkyl groups to the indium‐catalyzed reductive alkylation of indoles, a reliable and practical method capable of offering a wide range of alkylindoles with structural diversity has been developed. An important feature of this method is that the loading of the indium catalyst can be reduced by more than that of the original alkyne‐based system.
An iron‐promoted electrophilic annulation of aryl enynes with disulfides or diselenides has been developed. In the presence of iron(III) chloride (FeCl3) and iodine (I2,), a variety of trifluoromethyl‐containing aryl enynes underwent electrophilic annulation with various disulfides or diselenides successfully to afford the corresponding polysubstituted naphthalenes in moderate to excellent yields.
This paper discloses an iodine‐mediated C H thiolation strategy for introduction of dithiocarbamates onto imidazoheterocycles under mild conditions. Imidazole derivatives, including imidazopyridines, imidazothiazoles, and benzoimidazoles, were well tolerated to afford diverse imidazoheterocycles‐dithiocarbamates compounds. These compounds are expected to be significant for drug discovery.
A practical, nickel‐catalyzed Kumada‐type double cross‐coupling reaction of gem‐difluoroalkenes with 1,4‐ or 1,5‐di‐Grignard reagents was developed. The reaction proceeded efficiently at room temperature and a variety of cyclization products, arylmethylenecyclopentanes and arylmethylenecyclohexanes, were obtained in high to excellent yields, respectively.
Under zinc Lewis acid catalysis, terminal alkynes coupled dehydrogenatively with 1,8‐naphthalenediaminatoborane [HB(dan)]. It is important to note that the resulting alkynylboranes with an C(sp) B(dan) bond are isolable by column chromatography on silica gel (SiO2) and are usable as coupling partners for palladium‐ and copper‐catalyzed cross‐coupling reactions with (hetero)aryl halides.
A highly stereoselective three‐component Povarov reaction, catalyzed by (R)‐ and (S)‐BINOL hydrogen phosphate, was achieved for the first time with aminopyrroles and aminopyrazoles as 2‐azadiene precursors. A variety of aldehydes, enecarbamates, amino‐substituted azines participated in the reaction to afford the tetrahydropyrrolopyridines and tetrahydropyrazolopyridines in good yields with excellent diatereo‐ and enantioselectivities. A stereochemical model is proposed to account for the observed absolute stereochemistry.
