Lithium alkynylboronates alkylideneacetoacetates

The reactivity profiles of the boronate complexes are also diverse.43 For example, the lithium methyl-trialkylboronates (75) are inert, but the more reactive copper(I) methyltrialkylboronates (76) afford conjugate adducts with acrylonitrile and ethyl acrylate (Scheme 16).44 In contrast, the lithium alkynylboronates (77) are alkylated by powerful acceptors, such as alkylideneacetoacetates, alkylidene-malonates and a-nitroethylene, to afford the intermediate vinylboranes (78) to (80), which on oxidation (peracids) or protonolysis yield the corresponding ketones or alkenes, respectively (Scheme 17).45a Similarly, titanium tetrachloride-catalyzed alkynylboronate (77) additions to methyl vinyl ketone afford 1,5-diketones (81).4Sb Mechanistically, the alkynylboronate additions proceed by initial 3-attack of the electrophile and simultaneous alkyl migration from boron to the a-carbon. 

---

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

---