Divergence in the Aquilegia ecalcarata complex is correlated with geography and climate oscillations: Evidence from plastid genome data.

Quaternary climate oscillations and geographical heterogeneity play important roles in determining species and genetic diversity distribution patterns, but how these factors affect the migration and differentiation of East Asian plants species at the population level remains poorly understood. The Aquilegia ecalcarata complex, a group that originated in the Late Tertiary and is widely distributed throughout East Asia, displays high genetic variation that is suitable for studying elaborate phylogeographic patterns and demographic history related to the impact of Quaternary climate and geography. We used plastid genome data from 322 individuals in 60 populations of the A. ecalcarata complex to thoroughly explore the impact of Quaternary climate oscillations and geography on the phylogeographic patterns and demographic history of the A. ecalcarata complex through a series of phylogenetic, divergence time estimation, and demographic history analyses. The dry, cold climate and frequent climate oscillations that occurred during the early Pleistocene and the Mid-Pleistocene transition led to the differentiation of the A. ecalcarata complex, which was isolated in various areas. Geographically, the A. ecalcarata complex can be divided into Eastern and Western Clades and five subclades, which conform to the divergence of the East Asian flora. Our results clearly show the impact of Quaternary climate and geography on evolutionary history at the population level. These findings promote the understanding of the relationship between plant genetic differentiation and climate and geographical factors of East Asia at the population level.

Palladium-catalyzed alkylation of aryl C-H bonds with sp3 organotin reagents using benzoquinone as a crucial promoter.

The combination of directed C-H activation, batch-wise addition of tetraalkyltin reagents, and rate enhancement by benzoquinone and microwave irradiation provides a promising strategy for the direct coupling of C-H bonds with organometallic reagents. A variety of tetraalkyltins were coupled to C-H bonds to give the alkylated products in good yields by using 5 mol % Pd(OAc)2 as the catalyst. Benzoquinone was shown to be essential for the C-H activation when substrates containing non-pi-conjugated chelating groups are used. Monitoring the formation and reductive elimination of the Pd(Ar)(Me)L2 complex also revealed that benzoquinone promotes the reductive elimination step. Microwave irradiation enhances the reaction rate drastically. The versatility of this protocol was demonstrated by using substrates containing either oxazoline or pyridine as directing groups.