The enantiospecific and diastereocontrolled total synthesis of alkaloid (-)-217A is described that employs a stepwise [3+3] annelation strategy and a piperidine 2,3-cyclopropanation-ring opening reaction as the key steps.

Off and on: A nickel‐catalyzed benzannulation of alkynylboronates provides functionalized phenols with high levels of chemo‐ and regioselectively. While transmetalation of organoboron intermediate to organonickel does not occur during cycloaddition, it is “switched on” by addition of base, thus allowing a one‐pot benzannulation and cross‐coupling to be realized (see scheme; Pin=pinacolato, Ms=mesyl).

The room-temperature cobalt-catalyzed [4 + 2] cycloaddition of alkynylboronates and 1,3-dienes provides a convenient and general method for the synthesis of benzene-based aromatic boronic esters. Two complementary aromatization strategies involving in situ elimination and DDQ oxidation were explored, with the latter finding more generality. Finally, the potential of this technique to generate highly functionalized biaryls has been demonstrated via the synthesis of chiral (racemic) DMAP catalysts.

A Ni-catalyzed benzannulation reaction of cyclobutenones and alkynes provides a rapid synthesis of heavily substituted phenols. The regioselectivity of this reaction can be modulated by variation of substituents on the alkyne. Though the incorporation of Lewis basic donors provides modest selectivities, the use of aryl substituents can provide high levels of regiocontrol. Finally, alkynylboronates derived from alkyl-substituted acetylenes provide both high yields and regioselectivities. This study suggests that alkynes bearing one sp(2) - and one sp(3) -based substituent can undergo benzannulation with high levels of regiocontrol whereby the sp(3) -based group is incorporated ortho-to the phenolic OH.

A facile and efficient method for the synthesis of isoindoline, indane, and dihydroisobenzofuran derivatives has been developed through the application of a halogen‐bridged iridium(III) complex to the [2+2+2] cycloaddition of α,ω‐diynes with alkynes. The cycloaddition tolerates a broad range of substitution groups, such as alcohol, alkyl, ether, and halogen, and the chemistry can be extended to prepare the corresponding borylated fused arenes. The reaction shows that hindered starting materials are also good partners, which provide the desired fused arenes in good yields.