Transition-metal-catalyzed denitrogenative transannulation: converting triazoles into other heterocyclic systems

Abstract

Transition metal catalyzed denitrogenative transannulation of a triazole ring has recently received considerable attention as a new concept for the construction of diverse nitrogen-containing heterocyclic cores. This method allows a single-step synthesis of complex nitrogen heterocycles from easily available and cheap triazole precursors. In this Minireview, recent progress of the transition metal catalyzed denitrogenative transannulation of a triazole ring, which was discovered in 2007, is discussed.

Scheme 1

Closed/opened form equilibrium of pyridotriazoles.

Scheme 2

Rhodium carbenoid insersion into a Si–H bond.

Scheme 3

Transannulation of the pyridotriazole 3b with alkynes. pfb = perfluorobutyrate.

Scheme 4

Denitrogenative annulation of pyridotriazoles 3 with nitriles.

Scheme 5

Proposed mechanism for transannulation of pyridotriazoles 3 with alkynes and nitriles.

Scheme 6

Denitrogenative cyclopropanation of the N-sulfonyl-1,2,3-triazole 17a with styrene. DCE = 1,2-dichloroethane, oct = octanoate.

Scheme 7

Transannulation of N-sulfonyl-1,2,3-triazole 17a with benzonitrile employing microwave-assisted and conventional heating methods.

Scheme 8

Denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles 17 with nitriles. TMS = trimethylsilyl.

Scheme 9

Proposed mechanism for the transannulation of N-sulfonyl-1,2,3-triazoles 17 with nitriles.

Scheme 10

Nickel-catalyzed transannulation of the N-sulfonyl-1,2,3-triazoles 17 with internal alkynes. The yields are those of the isolated product. [a] [Ni(cod)₂] (15 mol%) and P(nBu)Ad₂ (30 mol%). [b] 110°C. Ad = adamantyl, cod = 1,5-cyclooctadiene.

Scheme 11

Proposed mechanism of the nickel-catalyzed denitrogenative transannulation of N-sulfonyl-1,2,3-triazole 17a with internal alkynes. Ts = 4-toluenesulfonyl.

Scheme 12

Rhodium-catalyzed denitrogenative transannulation of N-sulfonyl-1,2,3-triazoles 17b with terminal alkynes.

Scheme 13

Proposed mechanism for transannulation of N-sulfonyl-1,2,3-triazoles 17b with terminal alkynes.

Scheme 14

Semi-one-pot transannulation toward synthesis of pyrroles.

Scheme 15

Transannulation of the NH-1,2,3-triazoles 36 with styrenes. NTTL = N-1,8-naphthoyl-tert-leucine.

Scheme 16

Palladium-catalyzed transannulation versus the Larock indole synthesis.

Scheme 17

Palladium-catalyzed denitrogenative transannulation of the N-aroylbenzotriazoles 39a with internal alkynes.

Scheme 18

Proposed mechanism of the palladium-catalyzed transannulation of N-aroylbenzotriazoles 39a with internal alkynes.

Scheme 19

Nickel-catalyzed transannulation of the 1,2,3-benzotriazinones 47 with an internal symmetrical alkyne.

Scheme 20

Nickel-catalyzed denitrogenative transannulation of 1,2,3-benzotriazinones 47 with alkynes. pin = pinacol.

Scheme 21

Nickel-catalyzed denitrogenative transannulation of the 1,2,3-benzotriazinones 47a with allenes. dppbenz = 1,2-bis(diphenylphosphino) benzene.

Scheme 22

Scope of the nickel-catalyzed transannulation of 1,2,3-benzotriazinones 47b with allenes.

Scheme 23

Nickel-catalyzed denitrogenative transannulation of 1,2,3-benzotriazinones 47a with internal cyclic allene. See Scheme 29 for structure of (R,R)-Me-duphos.

Scheme 24

Enantioselective synthesis of isoquinolones.

Scheme 25

Transannulation of benzotriazinones with 1,3-dienes. dppf = 1,1′-bis(diphenylphosphino)ferrocene.

Scheme 26

Scope of transannulation of the benzotriazinones 47b with 1,3-dienes.

Scheme 27

Nickel-catalyzed denitrogenative transannulation with alkenes.

Scheme 28

Palladium-catalyzed transannulation with isocyanides. Cp = cyclopentadienyl.

Scheme 29

Transannulation of 1,2,3,4-benzothiatriazine-1,1(2H)-dioxide 64 with allenes in the presence of various chiral ligands.

Scheme 30

Transannulation of 1,2,3,4-benzothiatriazine-1,2(2H)-dioxide 64a with various allenes.