Nonrandom seed release is an important determinant of how far seeds disperse, but the mechanisms that promote wind-related seed release under varying atmospheric conditions are poorly understood. We explored the use of particle image velocimetry (PIV) to gain a better mechanistic understanding of seed release by visualizing the flow velocities and vorticity in a two-dimensional slice of air around inflorescences. Pilot data taken in a wind tunnel show gradients in air velocity at the top of Carduus nutans capitula that may contribute to lift generation. Additionally, von Kármán vortex streets (vortices of opposite spin that are shed from the wake of an object) were observed shedding from capitula, which cause lateral forces on capitula and increase turbulence downwind at other locations. Avenues for further research include using PIV to examine the mechanisms of seed release and dispersal in wind tunnels and in the field. We found PIV to be a promising method to further explore the mechanisms behind seed release in wind dispersed plants, and a technique rich with opportunities for collaborations between plant dispersal ecologists and fluid dynamics specialists.

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A modular synthesis of highly substituted 3azapyrroles has been developed using a three-step sequence comprising copper-catalyzed alkyne−azide cycloaddition (CuAAC), N−H bond insertion, and cyclodehydration. 1-Sulfonyl-1,2,3-triazoles (1-STs) can be accessed from common alkyne and sulfonyl azide building blocks by CuAAC using CuTC. Rhodium(II)-acetate-promoted 1-ST denitrogenation results in highly electrophilic rhodium azavinyl carbenes that, here, underwent insertion into the N−H bond of secondary α-aminoketones to form 1,2-aminoalkenes. These products were cyclized and dehydrated using BF 3 •OEt 2 into highly substituted 3-azapyrroles. The three steps (CuAAC, N−H bond insertion, and cyclodehydration) could be telescoped into a one-pot process. The method proved to be highly efficient and tolerated a wide range of substituents.

Strained eight-membered cyclic alkynes undergo rapid inverse electron demand cycloaddition with sulfonyl azides to give the corresponding 1 sulfonylcyclooctatriazoles in excellent yield. Treatment of these sulfonyltriazoles with a chiral rhodium(II)...

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Abstract1,1-Dibromoalkenes can be used as direct precursors to three classes of 5-substituted 1,2,3-triazoles. Three different approaches to 1,2,3-triazole products were developed, linked to the N1-substituent. Treatment of 1,1-dibromoalkenes with n-butyllithium and reaction with a sulfonyl azide gave 5-substituted 1-sulfonyl-1,2,3-triazoles. The use of lithium base followed by transmetalation to zinc and reaction with aryl azides allowed access to 1-aryl-1,2,3-triazoles. Finally, the use of EtMgBr as base and reaction with an alkyl azide formed 1-alkyl-1,2,3-triazoles.