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First selective direct mono-arylation of piperidines using ruthenium-catalyzed C-H activation.

Schwarz MC, Dastbaravardeh N, Kirchner K, Schnürch M, Mihovilovic MD - Monatsh. Chem. (2013)

Bottom Line: A Ru-catalyzed mono-arylation in α-position of saturated cyclic amines is reported employing a C-H activation protocol.Substitution of the pyridine directing group with a bulky group, e.g., trifluoromethyl in the 3-position, proved to be crucial to avoid bis-arylation.Additionally, the directing group can be cleaved, taking advantage of an unprecedented detrifluoromethylation reaction.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria.

ABSTRACT

Abstract: A Ru-catalyzed mono-arylation in α-position of saturated cyclic amines is reported employing a C-H activation protocol. Substitution of the pyridine directing group with a bulky group, e.g., trifluoromethyl in the 3-position, proved to be crucial to avoid bis-arylation. This highly selective transformation can be performed with different amines and arylboronate esters. Additionally, the directing group can be cleaved, taking advantage of an unprecedented detrifluoromethylation reaction.

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Mentions: Both 16 (as crude material) and 17 were subjected to the cleavage conditions of NH2NH2/AcOH (2.5/0.7 M in EtOH) at 120 °C for 2 h in a closed vial, but only the reaction of 17 gave the desired product 2-phenylpiperidine (18) as detected by GC–MS and 1H NMR of the crude product after basic extraction. Also other reaction parameters (changing the acid to trifluoroacetic acid, increasing the reaction time or temperature) to cleave the reduced directing group from 16 did not lead to formation of 18. Still, a new cleavage protocol was developed as shown in Scheme 3, providing the desired product 18 in 47 % yield. Hence, our deprotection protocol is competitive to the previously published removal procedure of the unsubstituted pyridine directing group, which was also cleaved in 47 % overall yield [36].


First selective direct mono-arylation of piperidines using ruthenium-catalyzed C-H activation.

Schwarz MC, Dastbaravardeh N, Kirchner K, Schnürch M, Mihovilovic MD - Monatsh. Chem. (2013)

© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4494768&req=5

Mentions: Both 16 (as crude material) and 17 were subjected to the cleavage conditions of NH2NH2/AcOH (2.5/0.7 M in EtOH) at 120 °C for 2 h in a closed vial, but only the reaction of 17 gave the desired product 2-phenylpiperidine (18) as detected by GC–MS and 1H NMR of the crude product after basic extraction. Also other reaction parameters (changing the acid to trifluoroacetic acid, increasing the reaction time or temperature) to cleave the reduced directing group from 16 did not lead to formation of 18. Still, a new cleavage protocol was developed as shown in Scheme 3, providing the desired product 18 in 47 % yield. Hence, our deprotection protocol is competitive to the previously published removal procedure of the unsubstituted pyridine directing group, which was also cleaved in 47 % overall yield [36].

Bottom Line: A Ru-catalyzed mono-arylation in α-position of saturated cyclic amines is reported employing a C-H activation protocol.Substitution of the pyridine directing group with a bulky group, e.g., trifluoromethyl in the 3-position, proved to be crucial to avoid bis-arylation.Additionally, the directing group can be cleaved, taking advantage of an unprecedented detrifluoromethylation reaction.

View Article: PubMed Central - PubMed

Affiliation: Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9/163-OC, 1060 Vienna, Austria.

ABSTRACT

Abstract: A Ru-catalyzed mono-arylation in α-position of saturated cyclic amines is reported employing a C-H activation protocol. Substitution of the pyridine directing group with a bulky group, e.g., trifluoromethyl in the 3-position, proved to be crucial to avoid bis-arylation. This highly selective transformation can be performed with different amines and arylboronate esters. Additionally, the directing group can be cleaved, taking advantage of an unprecedented detrifluoromethylation reaction.

No MeSH data available.


Related in: MedlinePlus