Dalton Transactions
Paper
(ddd, J = 14.2, 4.2, 2.8 Hz, 1 H), 2.78 (ddd, J = 14.0, 7.9, 3.5 Hz, sequentially added. After 15 minutes, bromo derivatives 5a–b
1 H), 2.53 (s, 3 H), 1.193 and 1.186 (s, 3H), 1.15 and 1.14 (s, (0.05 mmol), 4 (20 μL, 0.15 mmol, 3 equiv.) and 2,6-lutidine
3H). 13C NMR (100 MHz, CD3CN, two stereoisomers) δ 175.10 (12 μL, 0.1 mmol, 2 equiv.,) were then added. The reaction
and 175.08, 168.9, 168.8, 157.91 and 157.89, 156.32 and mixture was carefully degassed via freeze-pump thaw (three
156.31, 153.6, 152.35 and 152.33, 151.8, 151.7, 151.4, 150.52 times), and the vessel was refilled with argon. The mixture in
and 150.51, 150.54, 150.0, 147.1, 145.5, 145.4, 139.97 and the Schlenk tube was stirred and irradiated with blue LEDs.
139.95, 139.8, 139.7, 133.01 and 132.91, 131.81 and 131.79, After 24 h of irradiation, aq. HCl 1 M (2 mL) was added and
131.00 and 130.98, 130.0, 129.62, 129.59, 127.93, 127.88, the mixture was extracted with AcOEt (4 × 5 mL). The organic
127.80, 127.77, 126.99 and 126.97, 126.97 and 126.95, 126.33 phase was dried (Na2SO4), and concentrated under vacuum
and 126.31, 125.4, 125.0, 124.90 and 124.89, 124.14 and and the crude mixture was purified by flash-chromatography
124.13, 123.96 and 123.94, 121.3, 77.5, 60.23 and 60.20, 53.2, on silica.
38.92 and 38.86, 36.57 and 36.56, 29.01 and 28.99, 27.16,
6a. The title compound was isolated by flash column chrom-
21.92. HPLC-MS (ESI): 968 [M − PF6]+, 484 [2M − PF6 + H]+. atography (SiO2, cyclohexane/EtOAc 95/5) as colorless oil. Y =
HRMS (ESI/Flow Injection): calcd for C49H45IrN9O 968.3376; 84%, ee = 60%. ee before column purification was 70%. ee was
found 968.3379.
determined by chiral HPLC analysis using
a
Daicel
1
3b. Yellow solid, Y = 97%. H NMR (400 MHz, CD3CN, two Chiralpak®IC column: hexane/i-PrOH 90/10, flow rate 1.00 mL
stereoisomers) δ 8.42 (s, 1 H), 8.35 (s, 1 H), 8.04 (dd, J = 8.1, 3.1 min−1, 30 °C, λ = 210 nm: tmajor = 18.9 min, tminor = 14.7 min;
Hz, 2 H), 7.98 (s, 1 H), 7.92 (d, J = 5.7 Hz, 1 H), 7.88–7.73 (m, 5 1H NMR and 13C NMR were consistent with those reported in
H), 7.60 (t, J = 6.8 Hz, 1 H), 7.32 (d, J = 5.6 Hz, 1 H), 7.20 (d, J = the literature.11
5.7 Hz, 1 H), 7.16 (d, J = 8.4 Hz, 2 H), 7.07–6.97 (m, 4 H),
6b. The title compound was isolated by flash column chrom-
6.94–6.84 (m, 4 H), 6.27 (dd, J = 6.8, 5.3 Hz, 2 H), 5.74 (s, 2 H), atography (SiO2, cyclohexane/EtOAc 97/3) as colorless oil. Y =
5.13 (s, 2 H), 3.63 (s, 1 H), 3.02 (dd, J = 14.2, 3.8 Hz, 1 H), 77%, ee = 77%. ee before column purification was 80%. ee was
2.72–2.61 (m, 4 H), 2.52 (s, 3 H), 1.95 (dt, J = 5.0, 2.5 Hz, 1 H), determined by chiral HPLC analysis using
a
Daicel
1.20 (s, 6 H). 13C NMR (100 MHz, CD3CN, two stereoisomers) δ Chiralpak®IC column, hexane/i-PrOH 90/10, flow rate 1.00 mL
174.3, 168.42 and 168.35, 157.9, 157.5, 155.9, 153.1, 151.9, min−1, 30 °C, λ = 210 nm: tmajor = 17.8 min, tminor = 14.9 min;
151.31 and 151.25, 150.9, 150.13 and 150.09, 149.1, 145.2, 1H NMR and 13C NMR were consistent with those reported in
145.06 and 144.98, 139.53 and 139.50, 132.55 and 132.46, the literature.16b
132.2, 131.4, 131.35 and 131.33, 130.3, 127.8, 126.6, 125.87
and 125.85, 125.76, 124.49 and 124.45, 124.3, 123.51 and
123.48, 120.85 and 120.83, 115.6, 76.5, 62.4, 60.4, 52.8, 37.8,
Results and discussion
27.6, 25.5, 25.3, 21.5. HPLC-MS (ESI): 998 [M − PF6]+, 499 [2M
−
PF6
+
H]+. HRMS (ESI/Flow Injection): calcd for Due to the requirement of mild reaction conditions, copper-
C50H47IrN9O2 998.3482; found 998.3476.
mediated azide–alkyne cycloadditions (CuAACs) have been
3c. Yellow solid, Y = 90%. 1H NMR (400 MHz, CDCl3, two largely used to couple different groups onto ruthenium(II) poly-
stereoisomers) δ 8.59–8.36 (m, 2 H), 7.91–7.79 (m, 4 H), pyridyl-type sensitizers.25 Inspired by a recent work on the
7.82–7.70 (m, 4 H), 7.70–7.60 (m, 2 H), 7.54–7.47 (m, 2 H), preparation of artificial photosynthetic dendrimers,24 we
7.47–7.31 (m, 6 H), 7.24–7.18 (m, 6 H), 7.18–7.12 (m, 4 H), decided to bind the azido-substituted iridium photo-sensitizer
7.06–6.96 (m, 4 H), 6.94–6.22 (m, 2 H), 6.30–6.22 (m, 2 H), 5.76 (1) to some suitably functionalized representative organo-
(s, 1 H) and 4.97–4.84 (m, 1H), 4.77 (s, 1 H), 3.70–3.60 (m, 1 catalysts (2), exploiting a click-chemistry approach. The general
H), 3.46–3.73 (m, 1 H), 3.21–3.10 (m, 1 H), 3.01–2.83 (s, 1 H), retrosynthetic strategy used for the preparation of iridium
2.84–5.69 (m, 1 H), 2.58 and 2.54 (s, 3 H), 2.30–2.24 (s, 1 H), bifunctional photoaminocatalyst 3 through CuAAC is outlined
2.00–1.96 (s, 1 H), 1.77–1.63 (m, 4 H), 1.59–1.50 (m, 1 H), in Scheme 1.
0.20–0.35 (m, 1 H). 13C NMR (100 MHz, CD3CN, two stereoi-
Three different alkyne-functionalized organocatalysts 2a–c
somers) δ 168.47 and 168.41, 157.4, 156.0, 153.1, 151.9, 151.29 were chosen as reaction partners (Fig. 1). 2a and 2b were
and 151.22, 150.9, 150.1, 149.6, 145.05 and 144.99, 139.54 and derived from MacMillan imidazolidin-4-ones, while 2c from
139.49, 139.51, 132.56 and 132.47, 131.4, 130.3, 128.6, 128.3, Maruoka 2-triphenylmethyl pyrrolidine. The CuAAC of
127.7, 126.6, 125.9, 124.46 and 124.43, 123.5, 120.9, 52.7, 32.7, L-phenylalanine-derived imidazolidin-4-one 2a was recently
30.4, 30.2, 30.0, 27.0, 26.0, 23.4, 22.3, 21.5, 19.3. HPLC-MS performed for the preparation of a recyclable magnetic nano-
(ESI): 1135 [M − PF6]+, 568 [2M − PF6 + H]+. HRMS (ESI/Flow catalyst, employed in asymmetric 1,3-dipolar cycloadditions.26
Injection): calcd for C63H58IrN8O 1135.4363; found 1135.4359.
Similarly, L-tyrosine-derived imidazolidin-4-one 2b was used to
synthesize a recyclable pentaerythritol supported catalyst,
exploited in enantioselective Diels–Alder reactions27a and in
Photocatalytic alkylation of aldehydes, general procedure
In a Schlenk tube with a rotaflo stopcock under an argon atmo- the immobilization of the catalyst on siliceous mesocellular
sphere at r.t., catalysts 3a–c (0.005 mmol, 0.01 equiv.), a solu- foam.27b The propargylated derivative of (2S,3R)-3-hydroxy-2-
tion of trifluoromethanesulfonic acid (0.1
M in DMF, triphenylmethyl-pyrrolidine was recently used by us in a
0.005 mmol, 50 μL, 0.01 equiv.) and DMF (0.45 mL) were CuAAC to prepare a recyclable [60]fullerene-hybrid catalyst,
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Dalton Trans.