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A new method for the preparation of halocyclobutenes is described. The developed process involves the dehydration of halocyclobutanols by using tetrafluoroboric acid–diethyl ether complex in dichloromethane at room temperature. The process allows for high yields of halocyclobutenes to be achieved by using alcohols that do not trigger the formation of isomeric allylic halides. [ABSTRACT FROM AUTHOR]

This short review summarizes the latest advances in the cross-coupling reactions of double and triple electrophilic templates bearing halogen atoms and an activated C–O bond. Reactions involving the formation of a C–C bond as part of di-, tri-, and tetrasubstituted double bond systems are highlighted. 1 Introduction 2 Cross-Coupling Reactions of Halovinyl Tosylates 3 Cross-Coupling Reactions of Halovinyl Triflates 4 Cross-Coupling Reactions of Halovinyl Phosphates 5 Cross-Coupling Reactions of Halovinyl Esters 6 Conclusion [ABSTRACT FROM AUTHOR]

Despite recent tremendous progress in the synthesis of nonplanar chiral aromatics, and helicenes in particular, their conversion to half-sandwich or sandwich transition metal complexes still lags behind, although they represent an attractive family of modular and underexplored chiral architectures with a potential catalytic use. In this work, starting from various chiral helicene-indene proligands, we prepared the enantio- and diastereopure oxa[6]- and oxa[7]helicene-indenido half-sandwich RhI and RhIII complexes and oxa[7]helicene-bisindenido ansa-metallocene FeII complex. To document their use, oxahelicene-indenido half-sandwich RhIII complexes were employed as chiral catalysts in enantioselective C-H arylation of benzo[h]quinolines with 1-diazonaphthoquinones to afford a series of axially chiral biaryls in mostly good to high yields and in up to 96 : 4 er. Thus, we developed stereocontrolled synthesis of chiral helicene-indenido ansa- and half-sandwich metal complexes, successfully demonstrated the first use of such helicene Cp-related metal complexes in enantioselective catalysis, and described an unusual sequence of efficient central-to-helical-to-planar-to-axial chirality transfer., (© 2024 Wiley‐VCH GmbH.)

Cationic amidotitanocene complexes [Cp 2 Ti(NPhAr)][B(C 6 F 5 ) 4 ] (Cp=η 5 -C 5 H 5 ; Ar=phenyl (1 a), p-tolyl (1 b), p-anisyl (1 c)) were isolated. The bonding situation was studied by DFT (Density Functional Theory) using EDA-NOCV (Energy Decomposition Analysis with Natural Orbitals for Chemical Valence). The polar Ti-N bond in 1 a-c features an unusual inversion of σ and π bond strengths responsible for the balance between stability and reactivity in these coordinatively unsaturated species. In solution, 1 a-c undergo photolytic Ti-N cleavage to release Ti(III) species and aminyl radicals ⋅NPhAr. Reaction of 1 b with H 3 BNHMe 2 results in fast homolytic Ti-N cleavage to give [Cp 2 Ti(H 3 BNHMe 2 )][B(C 6 F 5 ) 4 ] (3). 1 a-c are highly active precatalysts in olefin hydrogenation and silanes/amines cross-dehydrogenative coupling, whilst 3 efficiently catalyzes amine-borane dehydrogenation. The mechanism of olefin hydrogenation was studied by DFT and the cooperative H 2 activation key step was disclosed using the Activation Strain Model (ASM)., (© 2021 Wiley-VCH GmbH.)