An Electrostatically-Anchored Rhodium(I) Catalyst for the Hydroformylation and Tandem Hydroformylation/Acetalization of Biorenewable Allyl Benzenes

Carvalho, Glenda A.; Gusevskaya, Elena V.; Santos, Eduardo N. dos

doi:10.5935/0103-5053.20140254

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Journal of the Brazilian Chemical Society

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Articles • J. Braz. Chem. Soc. 25 (12) • Dec 2014 • https://doi.org/10.5935/0103-5053.20140254 copy

An Electrostatically-Anchored Rhodium(I) Catalyst for the Hydroformylation and Tandem Hydroformylation/Acetalization of Biorenewable Allyl Benzenes

Authorship SCIMAGO INSTITUTIONS RANKINGS

A rhodium catalyst anchored in a commercial anion exchange resin (IRA900/TPPMS/Rh) was prepared straightforwardly through a simple protocol from readily available precursors. The material was used as a heterogeneous catalyst for the hydroformylation and tandem sequence hydroformylation/acetalization of eugenol and estragole under mild conditions. The regioselectivity for linear products was ca. 62%, but for the allyl benzenes the branched isomer are also valuable. The performance of the anchored catalyst in hydroformylation was comparable to that of the conventional homogeneous rhodium system; however, its efficiency in the acetalization step was significantly higher. The material can be separated from the reaction solutions by decantation and re-used without a significant loss in activity and selectivity. This simple catalytic method represents an economically attractive route to commercially valuable fragrance compounds starting from the substrates easily available from natural bio-renewable sources.

anchored rhodium catalyst; tandem; hydroformylation; acetalization

Run	Pressure CO:H₂ / atm	time^b b reaction time required for nearly complete conversion; / h	TOF^c c reaction rate (TOF - turnover frequency taken from the linear part of conversion vs. time plots); / h^-1	Selectivity^d d the rest of the mass balance was due to the hydrogenation product 2a. The regioselectivity for the linear product (4a) was ca. 62% in all runs; / % for the products of
Run	Pressure CO:H₂ / atm			hydroformylation (4a and 5a)	isomerization (2a)
1^e e 50 ºC;	30:30	24^f f 60% conversion;	14	60	22
2	30:30	15	63	94	5
3	20:20	15	68	82	12
4	40:40	15	68	95	5
5	40:20	24	42	89	10
6	20:40	7	174	90	9
7^g g runs 7 and 8 were the second and the third use of the catalyst separated after run 2.	30:30	17	50	92	7
8^g g runs 7 and 8 were the second and the third use of the catalyst separated after run 2.	30:30	15	55	91	8

Run	Substrate	Solvent	Conversion / %	Selectivity for hydroformylation^b b the rest of the mass balance was due to the hydrogenation and isomerization products, 2 and 3, respectively. The regioselectivity for the linear products (4 + 4') was ca. 62% in all runs; / %
Run	Substrate	Solvent	Conversion / %	Total	Aldehydes (4 and 5)	Acetals (4' and 5')
2	1a	toluene	99	94	94	0
9	1a	ethanol	96	94	17	77
10	1a	methanol	98	96	5	91
11^c c catalyst: [Rh(cod)(μ-OMe)]2 (5.0 × 10-3 mmol) and TPPMS (5.0 × 10-2 mmol) instead of IRA900/TPPMS/Rh. The reaction was nearly completed in 5 h;	1a	methanol	100	95	85	10
12^d d runs 12 and 13 were the first and the second re-using of the catalyst separated after run 10.	1a	methanol	96	97	9	88
13^d d runs 12 and 13 were the first and the second re-using of the catalyst separated after run 10.	1a	methanol	94	97	9	88
14	1b	methanol	94	99	21	71
15	2a	methanol	9	41	18	23

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