Stereoselective Palladium‐Catalyzed C−F Bond Alkynylation of Tetrasubstituted gem‐Difluoroalkenes

• Published in: Angewandte Chemie International Edition Vol. 59; no. 28; pp. 11293 - 11297
• Main Authors: Ma, Qiao, Wang, Yanhui, Tsui, Gavin Chit
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 06.07.2020; Wiley Subscription Services, Inc
• Edition: International ed. in English
• Subjects: Alkynes; Chelation; Chemistry; Chemistry, Multidisciplinary; Crystal structure; C−F bonds; fluoroalkenes; fluoroenynes; oxidative addition; Palladium; Physical Sciences; Science & Technology; Stereochemistry; Stereoselectivity; fluoroalkenes; ACTIVATION; DIFLUOROOLEFINATION; C-F bonds; DIAZO-COMPOUNDS; TMSCF3; HYDRODEFLUORINATION; FUNCTIONALIZATION; CROSS-COUPLING REACTIONS; fluoroenynes; ALPHA-FLUOROALKENYLATION; palladium; FLUORINE; oxidative addition; BORYLATION; C−F bonds
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202002219

A stereoselective Pd(PPh3)4‐catalyzed C−F bond alkynylation of tetrasubstituted gem‐difluoroalkenes with terminal alkynes has been developed. This method gives access to a great variety of conjugated monofluoroenynes bearing a tetrasubstituted alkene moiety with well‐defined stereochemistry. Chelation‐assisted oxidative addition of Pd to the C−F bond is proposed to account for the high level of stereocontrol. An X‐ray crystal structure of a key monofluorovinyl PdII intermediate has been obtained for the first time as evidence for the proposed mechanism. A stereoselective Pd(PPh3)4‐catalyzed C−F bond alkynylation of tetrasubstituted gem‐difluoroalkenes with terminal alkynes has been developed. This method gives access to a great variety of conjugated monofluoroenynes bearing a tetrasubstituted alkene moiety with well‐defined stereochemistry (E/Z>99:1). Chelation‐assisted oxidative addition of Pd to theC−F bond is proposed to account for the high level of stereocontrol.