Supramolecular capsules were assembled by neutral halogen bonding (XB) and studied in the solid state, in solution, and in the gas phase. The geometry of the highly organized capsules is shown by an X-ray crystal structure which features the assembly of two XB hemispheres, geometrically rigidified by H-bonding to eight MeOH molecules and encapsulation of two benzene guests. To enhance capsular association strength, tuning the XB donor is more efficient than tuning the XB acceptor, due to desolvation penalties in protic solvents, as shown for a tetraquinuclidine XB acceptor hemisphere. With a tetra(iodoethynyl) XB donor and a tetralutidine XB acceptor, the association in deuterated benzene/acetone/methanol 70:30:1 at 283 K reaches K =(2.11±0.39)×10 m (ΔG=-6.9±0.1 kcal mol ). The stability of the XB capsules in the gas phase was confirmed by electrospray ionization mass spectrometry (ESI-MS). A new guest binding site was uncovered within the elongated iodoethynyl capsule.

Palladium-catalyzed regio-and diastereoselective C À H functionalization with bromoalkynes and electronically unbiased olefins is reported. The picolinamide directing group enables the formation of putative 5 and 6-exo-metallacycles as intermediates to afford monoalkynylated products in up to 91 % yield in a stereospecific fashion. The systematic study reveals that substrates with a wide range of substituents on the olefin and bromoalkyne coupling partners are tolerated. Chemoselective transformations were demonstrated for the obtained amides, olefins, and alkynes. Conjugated 1,3-enynes are abundant in natural products, [*] B. Supporting information and the ORCID identification number for one of the authors of this article can be found under: https://doi.org/10.1002/anie.202000935. Scheme 2. Prior studies and challenges. TIPS = triisopropylsilyl. Angewandte Chemie Communications Scheme 5. Scope of alkynes. Yields and E/Z ratios are given of isolated products after purification. [a] Determined by 1 H NMR analysis of unpurified reaction mixture. [b] DCE used as solvent. [c] Thermal ellipsoids (100 K) shown at the 30 % probability level. Hydrogen atoms and disorder have been omitted for clarity. Boc = tert-butyloxycarbonyl, TBS = tert-butyldimethylsilyl. Scheme 6. Product derivatizations. TBAF = tetrabutylammonium fluoride. Angewandte Chemie Communications 7821

A palladium-catalyzed C–H iodination of unactivated alkenes is reported. A picolinamide directing group enables the regioselective functionalization of a wide array of olefins to furnish iodination products as single stereoisomers. Mechanistic investigations suggest the reversible formation of a six-membered alkenyl palladacycle intermediate through a turnover-limiting C–H activation.

The selective transition-metal-mediated activation of C­(sp2)–H bonds of allenes is a formidable challenge because of the competitive, intrinsic reactivity of cumulated double bonds. Herein, we report a Pd-catalyzed C–H alkenylation of electronically unbiased allenes, affording penta-1,2,4-triene products in up to 94% yield. A picolin­amide directing group enables the formation of putative allenyl-pallada­cycles, which subsequently participate in a turnover-limiting Heck-type reaction with electron-deficient alkene coupling partners. This mechanistic proposal is consistent with experimental and computational investigations. Additionally, we report for the first time the use of picolin­amide N,O-acetals as readily removable auxiliaries for C–H activation reactions, allowing the efficient alkenylation of allenyl carbinol derivatives. Successful removal of the directing groups without affecting the reactive penta-1,2,4-triene substructure of the products is demonstrated.

Herein, the first total synthesis and stereochemical assignment of (+)-broussonetine H are reported. The ambiguous stereocenters within different fragments were independently installed through asymmetric methods, namely a diastereo- and enantioselective, iridium-catalyzed spiroketalization and Brown allylation. Finally, convergent merging of the fragments enabled the synthesis of all potential diastereomers, allowing stereochemical assignment of (+)-broussonetine H.