Trindade et al.
7.09-6.97 (m, toluene), 3.81 (s, 2H), 3.72-3-69 (m, 8H),
2.09-2.08 (toluene), 1.32-1.30 (m, 24H), 1.09 (d, 12H); 13C NMR
(C7D8) δ (ppm) ) 188.29, 145.98, 139.02, 123.43, 54.40, 28.07,
25.31, 24.13. Anal. Calcd for C35H50N2O8Rh2: C, 50.49; H, 6.05;
N, 3.36. Found: C, 50.51; H, 6.47; N, 3.39. Additional NMR
experiments such as HMQC were carried out and confirmed the
characterization described.
General Procedure for the Evaluation of the in Situ
Methodology (Table 4). Rh2(pfb)4 (7.90 mg, 7.50 × 10-3 mmol,
3 mol %) was weighted into a flame-dried round-bottom flask
equipped with a condenser and under argon atmosphere. tert-Amyl
alcohol (0.5 mL) was added, the suspension was stirred at room
temperature for 5 min, and then phenylboronic acid (61.00 mg,
0.50 mmol), 1,3-bis(2,6-diisopropylphenyl)imidazolinium chloride
(3.20 mg, 7.50 × 10-3 mmol, 3 mol %), KOtBu (28.00 mg, 0.25
mmol), and the corresponding aldehyde (0.25 mmol) were succes-
sively added. The resulting mixture was stirred at 40, 60 or 80 °C
for different periods of time. The reaction mixture was concentrated
under reduced pressure and the residue was purified by preparative
thin-layer chromatography (ethyl acetate/hexane) to yield the desired
secondary alcohols.
General procedure for the Arylation of Aldehydes Using
Complex 27 as the Catalyst (Table 6). Complex 27 (3.00 mg,
2.50 × 10-3 mmol, 1 mol %) was weighted into a flame-dried
round-bottom flask equipped with a condenser and under argon
atmosphere. tert-Amyl alcohol (0.5 mL), phenylboronic acid (61.00
mg, 0.50 mmol), and KOtBu (2.80 mg, 0.025 mmol, 10 mol %)
were successively added, and the resulting suspension was stirred
at room temperature for 15 min after which the corresponding
aldehyde (0.25 mmol) were added. The resulting mixture was stirred
at 90 °C for different periods of time. The reaction mixture was
concentrated under reduced pressure, and the residue was purified
by preparative thin-layer chromatography (ethyl acetate/hexane) to
yield the desired secondary alcohols.
General Procedure for the Arylation of Aldehydes Using
Complex 28 as the Catalyst (Table 8). Complex 28 (3.00 mg,
2.50 × 10-3 mmol, 1 mol %) was weighted into a flame-dried
round-bottom flask equipped with a condenser and under argon
atmosphere. Methanol (0.5 mL), phenylboronic acid (61.00 mg,
0.50 mmol), and KOtBu (2.80 mg, 0.025 mmol, 10 mol %) were
successively added, and the resulting suspension was stirred at room
temperature for 15 min after which the corresponding aldehyde
(0.25 mmol) were added. The resulting mixture was stirred at 60
°C or reflux for different periods of time. The reaction mixture
was concentrated under reduced pressure, and the residue was
purified by preparative thin-layer chromatography (ethyl acetate/
hexane) to yield the desired secondarys.
temperature for 15 min after which the corresponding aldehyde
(0.25 mmol) were added. The resulting mixture was stirred at 60
°C or reflux for different periods of time. The reaction mixture
was concentrated under reduced pressure, and the residue was
purified by preparative thin-layer chromatography (ethyl acetate/
hexane) to yield the desired secondary alcohols.
Computational Details. All calculations were performed using
the Gaussian 03 software package,23 and the B3PW91 hybrid
functional, without symmetry constraints. That functional includes
a mixture of Hartree-Fock24 exchange with DFT17 exchange-
correlation, given by Becke’s three-parameter functional25 with
Perdew and Wang’s 1991 gradient-corrected correlation func-
tional.26 The LanL2DZ basis set27 augmented with an f-polarization
function28 was used for Rh and a standard 6-31G(d,p)29 for the
remaining elements. Transition-state optimizations were performed
with the synchronous transit-guided quasi-newton method (STQN)
developed by Schlegel et al.30 Frequency calculations were
performed to confirm the nature of the stationary points, yielding
one imaginary frequency for the transition states and none for the
minima. Each transition state was further confirmed by following
its vibrational mode downhill on both sides and obtaining the
minima presented on the energy profiles. A natural population
analysis (NPA)21 and the resulting Wiberg indices18 were used for
a detailed study of the electronic structure and bonding of the
optimized species. Energy values reported along the text result from
single point energy calculations with the solvent (methanol) effect
taken into account through the polarizable continuum model (PCM)
initially devised by Tomasi and co-workers31 as implemented on
Gaussian 0332 and, thus, can be taken as free energy.33 The
molecular cavity was based on the united atom topological model
applied on UAHF radii, optimized for the HF/6-31G(d) level.
Acknowledgment. We thank the Fundac¸a˜o para a Cieˆncia e
Tecnologia (POCI 2010) and FEDER (PTDC/QUI/66695/2006,
PTDC/QUI/66015/2006, POCI/QUI/60175/2004, POCI/QUI/
58791/2004, SFRH/BPD/18624/2004, and SFRH/BD/30619/
2006) for financial support.
Supporting Information Available: Tables with atomic
coordinates for all optimized species. This material is available
JO800087N
(25) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(26) (a) Burke, K.; Perdew, J. P.; Wang, Y. In Electronic Density Functional Theory:
Recent Progress and New Directions; Dobson, J. F., Vignale, G., Das, M. P., Eds.;
Plenum: New York, 1998. (b) Perdew, J. P. In Electronic Structure of Solids ’91, Ed.
Ziesche, P., Eschrig, H., Eds.; Akademie Verlag: Berlin, 1991; p 11. (c) Perdew, J. P.;
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General Procedure for the Arylation of Aldehydes Using
Complex 31 as the Catalyst (Table 10). Complex 31 (2.00 mg,
2.50 × 10-3 mmol, 1 mol %) was weighted into a flame-dried
round-bottom flask equipped with a condenser and under argon
atmosphere. Methanol (0.5 mL), phenylboronic acid (61.00 mg,
0.50 mmol), and KOH (1.40 mg, 0.025 mmol, 10 mol %) were
successively added, and the resulting suspension was stirred at room
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