Recyclable heterogeneous and low-loading homogeneous chiral imidazolidinone catalysts for α-alkylation of aldehydes

Article abstract of DOI:10.1002/cplu.201400030

Two polystyrene-supported and six homogeneous MacMillan imidazolidinone catalysts were prepared and tested for the asymmetric α-alkylation of propanal with benzodithiolylium tetrafluoroborate. The chiral imidazolidinone was linked to polystyrene through the N-3 atom or through the phenyl ring and their catalytic activity was compared with that of their unsupported precursors. This comparison has allowed us to find an unsupported catalyst that displays high catalytic activity down to 5 or 2 mol-% at room temperature with a high level of enantioselectivity also when used with hexanal and 3-phenylpropanal. In addition, one of the heterogeneous materials was revealed to be highly recyclable for at least eight cycles with no loss in efficiency working at the same levels of activity and enantioselectivity as the unsupported counterpart. Recycling drive: Is it possible to have a supported chiral imidazolidinone catalyst that is recyclable without loss in activity or a homogeneous counterpart catalytically active at low loading? We have investigated this topic using the α-alkylation of aldehydes as a benchmark reaction (see figure). Copyright

Full text of DOI:10.1002/cplu.201400030

Supporting Information
ꢀ Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2014
Recyclable Heterogeneous and Low-Loading
Homogeneous Chiral Imidazolidinone Catalysts for
a-Alkylation of Aldehydes
Anna Maria Pia Salvo, Francesco Giacalone, Renato Noto, and Michelangelo Gruttadauria*[a]
cplu_201400030_sm_miscellaneous_information.pdf

Content:
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1H and 13C NMR and IR spectra of catalysts 11-14
1H NMR spectra of known compounds 3 and 9
1H and 13C NMR and IR spectra of compound 8
HPLC of products 3, 8 and 9

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Figure S1. 1H NMR spectrum of compound 11.
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Figure S2. 13C NMR spectrum of compound 11.

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Figure S3. 1H NMR spectrum of compound 12.
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Figure S4. 13C NMR spectrum of compound 12.

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Figure S5. 1H NMR spectrum of compound 13.
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Figure S6. 13C NMR spectrum of compound 13.

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Figure S7. 1H NMR spectrum of compound 14.
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Figure S8. 13C NMR spectrum of compound 14.

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13

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Figure S9. IR spectra of compounds 11-14.
Figure S10. 1H NMR spectrum of compound 3.

Figure S11. 1H NMR spectrum of compound 9.
Figure S12. IR spectrum of compound 8.

Figure S13. 1H NMR spectrum of compound 8.
Figure S14. 13C NMR spectrum of compound 8.

Figure S15. Chromatogram of (S)-2-(benzo[d][1,3]dithiol-2-yl)propan-1-ol (3) obtained with
catalyst 14 (Table 3, entry 10).

Figure S16. Chromatogram of (S)-2-(benzo[d][1,3]dithiol-2-yl)propan-1-ol (3) obtained with
catalyst 13 (5 mol%) (Table 4, entry 9).

Figure S17. Chromatogram of (S)-2-(benzo[d][1,3]dithiol-2-yl)propan-1-ol (3) obtained with
catalyst 13 (20 mol%) (Table 4, entry 8).

Figure S18. Chromatogram of (S)-2-(benzo[d][1,3]dithiol-2-yl)hexan-1-ol (8) obtained with
catalyst 13 (Table 4, entry 15).

Figure S19. Chromatogram of (S)-2-(benzo[d][1,3]dithiol-2-yl)-3-phenylpropan-1-ol (9) obtained
with catalyst 13 (Table 4, entry 16).