Geminal Metalloid Substituents Enable Stereoselective Geometric Isomerization of Highly Substituted Alkenes via Energy-Transfer Catalysis
Year: 2026
Type: preprint
Abstract: Controlling alkene geometry with high stereochemical precision remains a fundamental challenge in synthetic chemistry, particularly for highly substituted systems. Here we report a stereoselective photoisomerization of gem-diborylalkenes in which visible light enables efficient E→Z interconversion of geminal metalloids-substituted carbon–carbon double bonds through a triplet energy-transfer (EnT) mechanism, overcoming the long-standing limitation of stereoselective photoisomerization of highly (tetra)substituted alkenes. A broad range of tri- and tetra-substituted alkenes are converted to the thermodynamically less stable Z-isomer with up to 99:1 selectivity. Mechanistic studies and density functional theory (DFT) calculations reveal that stereocontrol arises from both interplay between excited-state deconjugation due to steric bulkiness and substratephotocatalyst interactions. Sequential functionalizations of both geometrically defined diborylalkene isomers are also demonstrated, enabling the stereodivergent construction of complex stereodefined alkenes. Beyond facilitating stereoselective geometric isomerization of tri- and tetrasubstituted alkenes, this work establishes (gem)-dimetalloid alkenes as light-programmable scaffolds and introduces a general strategy for boron-mediated photochemical control of alkene stereochemistry with implications for molecular and materials design.
Source: ChemRxiv
Institutions: Hebrew University of Jerusalem, Westmont College
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Awards: G1117273162, G1453181110, Track 4: Advanced CI Coordination Ecosystem: Monitoring and Measurement Services, G3062527969, G3562386289, G3778588758, Track 1: ACCESS Resource Allocations Marketplace and Platform Services (RAMPS), G4010157413, ACO: An Open CI Ecosystem to Advance Scientific Discovery (OpenCI), Track 3: COre National Ecosystem for CyberinfrasTructure (CONECT), G5367127336, G5464919783, G5483133893, G8054376542, Track 2: Customized Multi-tier Assistance, Training, and Computational Help (MATCH) for End User ACCESS to CI
OpenAlex ID: W7214620968