Mechanistic studies on the Cu-catalyzed three-component reactions of sulfonyl azides, 1-alkynes and amines, alcohols, or water: dichotomy via a common pathway.
Combined analyses of experimental and computational studies on the Cu-catalyzed three-component reactions of sulfonyl azides, terminal alkynes and amines, alcohols, or water are described. A range of experimental data including product distribution ratio and trapping of key intermediates support the validity of a common pathway in the reaction of 1-alkynes and two distinct types of azides substituted with sulfonyl and aryl(alkyl) groups. The proposal that bimolecular cycloaddition reactions take place initially between triple bonds and sulfonyl azides to give N-sulfonyl triazolyl copper intermediates was verified by a trapping experiment. The main reason for the different outcome from reactions between sulfonyl and aryl(alkyl) azides is attributed to the lability of the N-sulfonyl triazolyl copper intermediates. These species are readily rearranged to another key intermediate, ketenimine, into which various nucleophiles such as amines, alcohols, or water add to afford the three-component coupled products: amidines, imidates, or amides, respectively. In addition, the proposed mechanistic framework is in good agreement with the obtained kinetics and competition studies. A computational study (B3LYP/LACV3P*+) was also performed confirming the proposed mechanistic pathway that the triazolyl copper intermediate plays as a branching point to dictate the product distribution.
Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea.
Eun Jeong
EJ
Yoo
Mårten
M
Ahlquist
Imhyuck
I
Bae
K Barry
KB
Sharpless
Valery V
VV
Fokin
Sukbok
S
Chang
D000438:Alcohols / Q000737:chemistry*; D000480:Alkynes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D001386:Azides / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D005030:Ethylenes / Q000737:chemistry; D007096:Imidoesters / Q000737:chemistry; D007536:Isomerism; D007659:Ketones / Q000737:chemistry; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D013457:Sulfur Compounds / Q000737:chemistry*; D013696:Temperature; D014230:Triazoles / Q000737:chemistry; D014867:Water / Q000737:chemistry*
D000438:Alcohols; D000480:Alkynes; D000588:Amines; D001386:Azides; D005030:Ethylenes; D007096:Imidoesters; D007659:Ketones; D013457:Sulfur Compounds; D014230:Triazoles; D014867:Water; D003300:Copper; C008223:ketene