Retraction: Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides.

Retraction of 'Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides' by Yingying Pan et al., Org. Biomol. Chem., 2019, 17, 4230-4233, https://doi.org/10.1039/C9OB00628A.

Ti-Catalyzed Dehydroxylation of Tertiary Alcohols.

Herein we report a Ti-catalyzed direct dehydroxylation of tertiary aliphatic alcohols under mild reaction conditions, forging Barton-type deoxygenation products. This protocol tolerates a wide range of functional groups, including primary alkyl chloride and carbonyl groups. It allows for selective dehydroxylation of tertiary alcohols in diols and the formation of deuterated products with moderate deuterium incorporation. The efficient modification of several drugs and natural products (or their derivatives) highlights the synthetic utility of this method.

Ni-Catalyzed Asymmetric Reductive Alkenylation of α-Chlorosulfones with Vinyl Bromides.

A nickel-catalyzed enantioconvergent reductive cross-coupling of α-chlorosulfones with vinyl bromides is described here. This strategy enables the enantioselective construction of chiral allylic sulfones from simple α-chlorosulfones and vinyl bromides. The mild reaction conditions lead to excellent functional group compatibility, as evidenced by the broad substrate scope and tolerance of complex bioactive molecules. Our preliminary mechanistic study suggests that this enantioselective vinylation process operates through a radical intermediate.

Diverse Synthesis of Chiral Trifluoromethylated Alkanes via Nickel-Catalyzed Enantioconvergent Reductive Hydroalkylation of Unactivated Olefins.

Here, we report a nickel-catalyzed enantioconvergent hydroalkylation of olefins with trifluoromethyl-containing α-alkyl halides for the synthesis of enantioenriched trifluoromethylated alkanes. This reaction employs readily available and bench-stable alkenes as alkyl coupling partners, featuring mild conditions, a broad substrate scope, and high functional group tolerance. The synthetic utility of this method is further demonstrated in the late-stage functionalization of a range of drug molecules and natural products.

Ni-Catalyzed Cross-Electrophile Coupling of Aryl Triflates with Thiocarbonates via C-O/C-O Bond Cleavage.

A nickel-catalyzed reductive coupling of aryl triflates with thiocarbonates is reported here. Both electron-rich and -deficient aryl C(sp2)-O electrophiles as well as a class of O-tBu S-alkyl thiocarbonates are compatible with the optimized reaction conditions, as evidenced by 49 examples. The reaction also proceeds with good chemoselective cleavage of the C-O bond with regard to thioesters. This work broadens the scope of nickel-catalyzed reductive cross-electrophile coupling reactions.

Zn- and Cu-Catalyzed Coupling of Tertiary Alkyl Bromides and Oxalates to Forge Challenging C-O, C-S, and C-N Bonds.

We describe here the facile construction of sterically hindered tertiary alkyl ethers and thioethers via the Zn(OTf)2-catalyzed coupling of alcohols/phenols with unactivated tertiary alkyl bromides and the Cu(OTf)2-catalyzed thiolation of unactivated tertiary alkyl oxalates with thiols. The present protocol represents one of the most effective unactivated tertiary C(sp3)-heteroatom bond-forming conditions via readily accessible Lewis acid catalysis that is surprisingly less developed.

Formation of allylated quaternary carbon centers via C-O/C-O bond fragmentation of oxalates and allyl carbonates.

Disclosed herein emphasizes Fe-promoted cross-electrophile allylation of tertiary alkyl oxalates with allyl carbonates that generates all C(sp3)-quaternary centers. The reaction involves fragmentation of tertiary alkyl oxalate C-O bonds to give tertiary alkyl radical intermediates, addition of the radicals to less hindered alkene terminals, and subsequent cleavage of the allyl C-O bonds. Allylation with 2-aryl substituted allyl carbonates was mediated by Zn/MgCl2, and Fe is used to promote the radical addition efficiency. By introduction of activated alkenes, a three-component radical cascade reaction took place.

Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides.

This work describes Ni-catalyzed cross-electrophile coupling of benzyl chloroformate derivatives with aryl iodides that generates a wide range of diaryl methane products. The mild reaction conditions merit the C-O bond radical fragmentation of benzyl chloroformates via halide abstraction or a single electron reduction by a Ni catalyst. This work offers a new substrate type for cross-electrophile couplings.

Ni-catalyzed reductive addition of alkyl halides to isocyanides.

This paper highlights Ni-catalyzed reductive trapping of secondary and tertiary alkyl radicals with both electron-rich and electron-deficient aryl isocyanides using zinc as the terminal reductant, affording 6-alkylated phenanthridine in good yields. The employment of carbene ligands necessitates the alkyl radical process, and represents the first utility in the Ni-catalyzed reductive conditions for the generation of unactivated alkyl radicals from the halide precursors.

Nickel and cobalt-catalyzed coupling of alkyl halides with alkenes via heck reactions and radical conjugate addition.

Cross-coupling of alkyl halides with alkenes leading to Heck-type and addition products is summarized. The development of Heck reaction with aliphatic halides although has made significant progress in the past decade and particularly recently, it was much less explored in comparison with the aryl halides. The use of Ni- and Co-catalyzed protocols allowed efficient Heck coupling of activated and unactivated alkenes with 1°, 2° and 3° alkyl halides. In addition, radical conjugate addition to activated alkenes has become a well-established method that has led to efficient construction of many natural products. The utilization of Ni- and Co-catalyzed strategies would avoid toxic tin reagents, and therefore worth exploring. The recent development of Ni- and Co-catalyzed addition of alkyl halides to alkenes displays much improved reactivity and functional group tolerance. In this mini-review, we also attempt to overview the mechanisms that are proposed in the reactions, aiming at providing insight into the nickel and cobalt-catalyzed coupling of alkyl halides with alkenes.