Coumarins by Direct Annulation: β-Borylacrylates as Ambiphilic C3-Synthons
Modular β-borylacrylates have been validated as programmable, ambiphilic C3-synthons in the cascade annulation of 2-halo-phenol derivatives to generate structurally and electronically diverse coumarins. Key to this [3+3] disconnection is the BPin unit which serves a dual purpose as both a traceless linker for C(sp2)–C(sp2) coupling, and as a chromophore extension to enable inversion of the alkene geometry via selective energy transfer catalysis. Mild isomerisation is a pre-condition to access 3-substituted coumarins and provides a handle for divergence. The method is showcased in the synthesis of representative natural products that contain this venerable chemotype. Facile entry into π-expanded estrone derivatives modified at the A-ring is disclosed to demonstrate the potential of the method in bioassay development or in drug repurposing.
Wienhold, Max,Molloy, John J.,Daniliuc, Constantin G.,Gilmour, Ryan
supporting information
p. 685 - 689
(2020/11/30)
Synthesis and properties of germa-γ-lactones
Trialkylgermylpropanoic acids treated with 1 mole of bromine afford the monobromopropanoic acids, which are converted into the corresponding germa-γ-lactones in good yields by hydrolysis.The physical, chemical, and biological properties of these compounds are described.