Selective isomerization of α-pinene oxide to campholenic aldehyde by ionic liquid-supported indenyl-molybdenum(II)-bipyridine complexes


Campholenic aldehyde (CPA), an important flavor and fragrance intermediate, can be obtained by the Lewis acid-catalyzed isomerization of alpha-pinene oxide (PinOx), although achieving high yields ( > 90%) is a difficult challenge due to the high reactivity of the epoxide. In the present work, indenyl-molybdenum(II)bipyridine complexes [IndMo(bipy R )(CO) 2 ](BF 4 ) (bipy R = 2,2 ' -bipyridine (R = H ) or 4,4 ' -disubstituted2,2 ' -bipyridine) have been combined with various ionic liquid solvents to develop an efficient process for the selective conversion of PinOx to CPA under mild (35 degrees C) conditions. Excellent CPA yields (95%) were repeatedly obtained within 1 min reaction time for the easily recyclable catalytic system comprising [IndMo(4,4 ' -dinonyl-2,2 ' -bipyridine)(CO) 2 ](BF 4 ) and choline bis(trifluoromethylsulfonyl)imide.(c) 2022 Elsevier B.V. All rights reserved.



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Bruno, SM; Pillinger, M; Valente, AA; Goncalves, IS

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We acknowledge funding provided within the project CICECO - Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/ and LA/P/0006/2020, and the CENTRO 2020 Regional Operational Programme (project references CENTRO-01-0145-FEDER028031 and PTDC/QUIQOR/28031/2017), financed by national funds through the FCT (Fundacao para a Ciencia e a Tecnologia)/MEC (Ministerio da Educacao e Ciencia) (PIDDAC) and when appropriate co-financed by the European Union through the European Regional Development Fund under the Portugal 2020 Partnership Agreement. The costs associated with the position held by S.M.B. were funded by national funds (OE), through the FCT, in the scope of the framework contract foreseen in numbers 4, 5 and 6 of article 23 of the Decree-Law 57/2016 of August 29, changed by Law 57/2017 of July 19.

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