Alkyne Linchpin Strategy for Drug:Pharmacophore Conjugation: Experimental and Computational Realization of a Meta-Selective Inverse Sonogashira Coupling

The late-stage functionalization (LSF) of pharmaceutical and agrochemical compounds by the site-selective activation of C-H bonds provides access to diverse structural analogs and expands synthetically-accessible chemical space. We report a C-H functionalization LSF strategy that hinges on the use of an alkyne linchpin to assemble conjugates of sp²-rich marketed pharmaceuticals and agrochemicals with sp³-rich 3D fragments and natural products. This is accomplished through a template-assisted inverse Sonogashira reaction that displays high levels of selectivity for the meta position. This protocol is also amenable to distal structural modifications of α-amino acids. The transformation of alkyne functionality to other functional groups further highlights the applicative potential. Computational and experimental mechanistic studies shed light on the detailed mechanism. Turnover-limiting 1,2-migratory insertion of the bromoalkyne coupling partner occurs after relatively fast C-H activation. While this insertion occurs unselectively, regioconvergence results from one of the adducts undergoing a 1,2-trialkylsilyl migration to form the alkynylated product. A heterobimetallic Pd-Ag transition structure is essential for product formation in the β-bromide elimination step.

Synthesis of unsymmetrical diarylmethanols via C–Si bond bifunctionalization enabled by sequential [1,4]-Csp2 to O-silyl migration

Unsymmetrical C–Si bond bifunctionalization of 2,2′-bis(trimethylsilyl) diphenylmethanol via “on–off–on” sequential [1,4]-Csp² to O-silyl migration installs Csp³/Csp³, Csp³/Csp² or Csp²/Csp³ in one pot, giving sterically congested unsymmetrical diarylmethanols in good yields.

Diversity-oriented stereoselective synthesis of β,γ-disubstituted tert-homoallylic alcohols

The successive treatment of β-(trimethylsilyl)allyl phenyl sulfides with titanocene(II)-1-butene complex and ketones produced tertiary γ-(trimethylsilyl)homoallylic alcohols with good anti-selectivity, which reacted with a variety of organic halides in the presence of copper(I) tert-butoxide to afford the cross-coupling products, γ-substituted homoallylic alcohols.

Copper(i) 2-hydroxyethoxide-promoted cross-coupling of aryl- and alkenyldimethylsilanes with organic halides

The fluoride free cross-coupling between aryldimethylsilanes and organic halides proceeded in the presence of monocopper(i) alkoxide of ethylene glycol. The similar reaction of alkenyldimethylsilanes also took place with complete retention of configuration.

Diversity-oriented synthesis leads to an effective class of bifunctional linchpins uniting anion relay chemistry (ARC) with benzyne reactivity

In conjunction with the construction of a diversity-oriented synthesis library of 10-membered ring "natural product-like" macrolides, the design, synthesis, and validation of a unique class of bifunctional linchpins, uniting benzyne reactivity initiated by type II anion relay chemistry (ARC) has been achieved, permitting access to diverse [2+2], [3+2], and [4+2] cycloadducts.