A new synthetic platform accessing stereoregular polar polyolefins is introduced. We showcase the stability of aromatic azaborine derivatives by demonstrating the syndioselective polymerization of BN 2-vinylnaphthalene (BN2VN) by a monocyclopentadienyl titanium complex. Homogeneous early transition metal catalysts are well-established systems for the synthesis of highly stereoregular syndiotactic polystyrene (sPS), but the oxophilic nature of these complexes results in catalyst decomposition with polar monomers. BN2VN's compatibility with coordination polymerization, and its ability to intercept the mechanism of styrene polymerization, is attributed to its aromaticity. Stereoretentive postpolymerization oxidation of the organoborane side chain generates syndiotactic poly(vinyl alcohol) (sPVA), an example of PBN2VN's potential for diverse postfunctionalization.

Enantioenriched benzyl esters of propiolic acids undergo highly stereospecific decarboxylative coupling to provide 1,1-diarylethynyl methanes. This sp-sp(3) coupling does not require strongly basic conditions or preformed organometallics and produces CO2 as the sole byproduct. Ultimately, this method results in the successful transfer of stereochemical information from secondary benzyl alcohols to generate enantioenriched tertiary diarylmethanes.

We report the first example of a palladium-catalyzed decarboxylative dearomatization reaction that occurs via Pd-π-benzyl intermediates. In fact, the Pd-catalyzed decarboxylative cross-coupling reaction of benzyl enol carbonates can lead to either the dearomatized alicyclic ketones or α-monoarylated ketone products depending on the catalyst and ligand employed.

Benzylic alkylation of enolates and acetylides has been achieved through the use of a decarboxylative benzylation strategy. Previous research in this area is often limited by the need for extended conjugation in the electrophiles that are coupled. Herein, we report that the use of 1,1'-bis(diphenylphosphino)ferrocene (dppf) ligand allows the coupling of simple benzyl electrophiles with enolates, while the use of XPhos ligand promotes the decarboxylative couplings of propiolates.

Palladium-Catalyzed Stereospecific Decarboxylative Benzylation of Alkynes. -The highly stereospecific decarboxylative coupling of benzylic esters of propiolic acids to 1,1'-diarylethinyl methanes is described. The reaction tolerates aryl and alkyl substituted alkyne moieties. Aryl substituents equipped with strongly electron-withdrawing groups lead to the formation of allene isomers of the desired products. -(MENDIS, S. N.; TUNGE*, J. A.; Org. Lett. 17 (2015) 21, 5164-5167, http://dx.