Functionalization of C n H 2 n +2 Alkanes: Supercritical Carbon Dioxide Enhances the Reactivity towards Primary Carbon–Hydrogen Bonds

• Published in: ChemCatChem 2015-10, Vol.7 (20), p.3254-3260
• Main Authors: Gava, Riccardo, Olmos, Andrea, Noverges, Bárbara, Varea, Teresa, Funes‐Ardoiz, Ignacio, Belderrain, Tomás R., Caballero, Ana, Maseras, Feliu, Asensio, Gregorio, Pérez, Pedro J.
• Format: Article
• Language: English
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201500610

The functionalization of the primary sites of alkanes is one of the more challenging areas in catalysis. In this context, a novel effect has been discovered that is responsible for an enhancement in the reactivity of the primary C−H bonds of alkanes in a catalytic system. The copper complex Cu(NCMe) ( =hydrotris{[3,5‐bis(trifluoromethyl)‐4‐bromo]‐pyrazol‐1‐yl}borate) catalyzes the functionalization of C n H 2 n +2 with ethyl diazoacetate upon inserting the CHCO 2 Et unit into C−H bonds. In addition, the selectivity of the reaction toward the primary sites significantly increased relative to that obtained in neat alkane upon using supercritical carbon dioxide as the reaction medium. This was attributed to the effect of the carbon dioxide molecules that withdraw electron density from the fluorine atoms of the ligand, which enhances the electrophilic nature of the metal center. DFT studies validated this proposal.