Acylation of Grignard reagents mediated by N-methylpyrrolidone: A remarkable selectivity for the synthesis of ketones

Article abstract of DOI:10.1039/c1ob05780d

An efficient user-friendly method of acylation of Grignard reagents to selectively synthesize ketones is presented, which is assisted by simple amides such as NMP, or DMF. The present chemoselective method tolerates a variety of functional groups such as ketone, ester, nitrile and other functional groups.

Full text of DOI:10.1039/c1ob05780d

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Electronic Supporting Information
Acylation of Grignard reagents mediated by N-methylpyrrolidone: A
remarkable selectivity for the synthesis of ketones
Maravanhalli Sidde Gowda† Sushanth Sudhir Pande,§ Ramesha Andagar Ramakrishna,*, † and
Kandikere Ramaiah Prabhu*,§
†R. L. Fine Chem, No. 15, KHB Industrial Area, Yelahanka Newtown, Bangalore-560 106, Karnataka,
India
§Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, Karnataka, India
E-mails: prabhu@orgchem.iisc.ernet.in; ramesha63@hotmail.com
Table of Contents
Table of Contents
Page No
General
ESI 2
ESI 2 – ESI 3
ESI 4-ESI 17
ESI 18-ESI 19
ESI 20- ESI 45
Experimental Section
Analytical Data
References
1H and 13C spectra

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General. All solvents were dried and distilled according to standard methods before use. NMR spectra
were recorded on a JEOL LA-300, BRUKER-AV400 spectrometer in CDCl3 and DMSO-d6.
Tetramethylsilane (TMS; δ = 0.00 ppm) and residual non-deuterated DMSO signal (δ = 2.49 ppm) served
as internal standards for 1H NMR. The corresponding residual non-deuterated solvent signal (CDCl3: δ =
77.00 ppm; DMSO: δ = 39.50 ppm) was used as internal standards for 13C NMR. IR spectra were
measured using a JASCO FT/IR-410 spectrometer, and Perkin-Elmer FT/IR Spectrum BX, GX. Mass
spectra were measured with Micromass Q-Tof (ESI-HRMS), and GCMS shimadzu. Column
chromatography was conducted on Silica gel 230-400 mesh (Merck) and preparative thin-layer
chromatography was carried out using SILICA GEL GF-254. Elemental analysis was carried out at the
Department of Organic Chemistry, Indian Institute of Science, Bangalore, India by using Thermo
Finnigan Flash 1112 series analyser.
Experimental Section
Typical procedure adapted to preparation of Grignard Reagents. To a well-stirred dry mixture of
Mg (23.1 mmol) in dry THF (10 mL) in nitrogen atmosphere was added iodine (20 mg) and 1,2-
dibromoethane (100 mg), and the reaction mixture was heated to 55 - 60°. To this reaction mixture was
added aryl or alkyl bromide (23.1 mmol) in toluene (10 mL) at the same temperature and the reaction
mixture was stirred at 60°C for 1h and brought to room temperature and used for the next step.
Acylation of Grignard reagent (general procedure). To a well-stirred solution of NMP (2.51 g, 2.45
mL, 25.4 mmol) in dry toluene (10 mL) was added acid chloride (27.7 mmol) in toluene (10 mL) at 0 ºC
during 15 min, and stirred for 15 min at the same temperature, followed by the addition of RMgX (23.1
mmol, in 20 mL THF) at -5 to -10 ºC during 15 min. The reaction mixture was stirred for 4h at 0 to -5 ºC,
and was added to aqueous ammonium chloride solution (10g solution in 30 mL water), and extracted with
CH2Cl2 (3 × 50 mL ), the combined organic layer was washed with dil HCl (20%, 100mL), saturated
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Na2CO3 solution (100mL), and water (2 × 50 mL), dried over Na2SO4 and concentrated in vacuo. The
resulting crude mixture was purified by column chromatography to furnish the pure compound.
General procedure 2 (For compound 14c and 15c Table 2).
Step 1: To a well-stirred mixture of Mg (878 mg, 36 mmol) and I2 (100 mg) in THF (25 mL) was added
isobutyl chloride (3.22g, 3.65 g, 35 mmol) at room temperature during 20 min, heated at reflux for 1h,
cooled to 0 ° in N2 atmosphere and was added 2-bromopyridine (5g, 3.01 mL, 31.8 mmol, ) in toluene (6
mL) at 0 °C and stirred at the same temperature for 30 min to generate the Grignard reagent.
Step 2: To a well-stirred cold solution (0 °C) of NMP (3.4mL, 3.47 g, 35 mmol) in dry toluene (10 mL)
was added a solution of acid chloride (38.2 mmol, 1.2 equiv) in dry toluene (10 mL) during 15 min. After
stirring the reaction mixture for 15 min at the same temperature was added a solution of RMgX (31.8
mmol) in THF (generated in step 1) at -5 to -10 ºC during 15 min and the reaction mixture was stirred for
4 h at the same temperature and was quenched with aqueous ammonium chloride (10 g solution in 30 mL
water), extracted with CH2Cl2 (3 × 50 mL ), combined organic layer was separated and dried over
sodium sulphate and the solvent was removed completely. The residue was purified by column
chromatography on silica gel to obtain the product.
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Analytical Data.
Hexanophenone (1c).1 1H NMR (CDCl3, 400 MHz); Colourless liquid: IR (Neat, cm-1) = 1684; 7.94-
7.96 (m, 2H), 7.51-7.55 (m, 1H), 7.42-7.46 (m, 2H), 2.95 (t, 2H, J = 7.4 Hz), 1.73 (t, 2H, J = 7.4 Hz),
1.25-1.41(m, 4H), δ 0.90 (t, 3H, J = 6.8 Hz); 13C NMR (CDCl3, 75 MHz): δ 200.4, 136.9, 132.7, 128.4,
127.9, 38.4, 31.4, 23.9, 22.4, 13.8; HRMS(ESI) calculated for C12H16O: 177.1279, found 177.1278
(M+H).
4-chloro-1-(4-fluorophenyl)butan-1-one (2c).2 Prepared from p-fluorophenylmagnesium bromide and
4-chlorobutryl chloride as described in general procedure 1. Colorless liquid; IR (Neat, cm-1): 2964, 1687,
1H NMR (CDCl3, 400 MHz); δ 7.90 - 8.00 (m, 2H), 7.0 - 7.10 (m, 2H,), 3.68 (t, 2H, J = 6.2 Hz), 3.16 (t,
2H, J = 6.9 Hz), 2.22 (quintet, 2H, J = 6.4 Hz); 13C NMR (CDCl3, 75 MHz): δ 197.2, 166.9, 164.4, 133.0,
130.5, 130.4, 115.7, 115.5, 35.0, 31.0, 26.5; MS (EI) m/z 201(M+)
4-Chloro-1-(4-chlorophenyl)butan-1-one (3c).3 Prepared from p-chlorophenyl magnesium bromide
and 4-chlorobutryl chloride as described in general procedure 1. mp: 31 oC (29-30 oC)lit, 3a, Yield: 70%;
colourless solid; IR (Neat, cm-1) : 2961, 1686, 1H NMR (CDCl3, 400 MHz); δ 7.90 - 7.94 (m, 2H), 7.43 -
7.46 (m, 2H), 3.68 (t, 2H, J = 6.4 Hz), 3.16 (t, 2H, J = 7.2 Hz), 2.23 (p, 2H, J = 6.8 Hz); 13C NMR
(CDCl3, 75 MHz): δ 197.7, 139.6, 135.0, 129.4, 128.9, 44.5, 35.2, 26.6; MS (EI) m/z 217 (M+).
Benzophenone (4c).4 Prepared from benzoyl chloride and phenylmagnesium bromide as described in
general procedure 1. mp: 48 oC(47.5 oC)lit, 4a; Yield: 85%; Colourless solid; IR (KBr, cm-1): 1659, 1H
NMR (CDCl3, 300 MHz): δ 7.42-7.81(m, 10H), 13C NMR (CDCl3, 75 MHz): δ 196.5, 137.5, 132.3,
129.9,128.1; MS (EI) m/z 182 (M+); HRESI-MS (m/z): calculated for C13H10O: 183.0810, found 183.0812
(M+H).
4-Fluoro benzophenone (5c).5 Prepared from benzoyl chloride and fluoro-p-phenylmagnesium
bromide as described in general procedure 1. mp: 46-47 oC (45-47 oC)lit, 5a; Yield: 77%; pale yellow solid;
IR (KBr, cm-1):1723, 1660, 1H NMR (CDCl3, 400 MHz): δ 7.10 - 7.80 (m, 9H), 13C NMR (CDCl3, 100
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MHz): δ 195.2, 164.4(d, J = 252 Hz), 137.4, 133.7(d, J = 3 Hz), 132.6 (d, J= 9 Hz),132.4, 129.8, 128.3,
115.4 (d, J = 22 Hz), MS (EI) m/z 200(M+).
4-Methoxybenzophenone (6c).6Prepared from p-methoxybenzoyl chloride and phenylmagnesium
bromide as described in general procedure 1. mp: 58-60 oC (59-60 oC)lit, 6a; Yield: 76%; Colurless solid;
IR (Neat, cm-1) : 3059, 1651, 1H NMR (CDCl3, 300 MHz): δ ), 6.9 - 7.85 (m, 9H), 3.89 (s, 3H); 13C NMR
(CDCl3, 75 MHz): δ 195.5, 163.2, 138.2, 132.5, 131.8, 130, 129.6, 128.1, 113.5, 55.5, MS (EI) m/z
212(M+); HRESI-MS (m/z): calculated for C14H12O2: 213.0916, found 213.0915 (M+H).
2,4-Dichlorobenzophenone (7c).7 Prepared from 2,4-dichlorobenzoyl chloride and phenylmagnesium
bromide as described in general procedure 1. mp: 51-52 oC (50.5-51.5 oC)lit, 10a; Yield: 78%; Colourless
solid; IR (KBr, cm-1): 1680, 1673, 1H NMR (CDCl3, 400 MHz): δ 7.20 - 7.90 (m, 8H), 13C NMR (CDCl3,
100 MHz): δ 194.1, 136.8, 136.5, 136.1, 133.8, 132.3, 130.0, 129.9, 128.6, 127; MS (EI) m/z 250(M+);
HRESI-MS (m/z): calculated for C13H8Cl2O(M+Na) : 272.9850, found 272.9852 (M+Na).
Acetophenone (8c).8 Prepared from acetyl chloride and phenyl magnesium bromide as described in
general procedure 1. Yield: 72%; Colorless liquid; IR (Neat cm-1): 1684, 1H NMR (CDCl3, 400 MHz): δ
7.43-7.96 (m, 5H), 2.60 (s, 3H); 13C NMR (CDCl3, 100 MHz): δ 198.1, 137, 133, 128.5, 128.2, 26.5; MS
(EI) m/z 120(M+).
1-(4-chlorophenyl)ethanone (9c).9 Prepared from p-chlorophenyl magnesium bromide and acetyl
chloride as described in general procedure 1. Yield: 83%; colorless liquid; IR (Neat, cm-1): 1742, 1687,
1H NMR (CDCl3, 400 MHz): δ 7.87 - 7.89 (d, J = 8.2 Hz, 2H), 7.41 - 7.43 (d, J = 8.2 Hz, 2H), 2.58 (s,
3H); 13C NMR (CDCl3, 75 MHz): δ 196.7, 139.4, 135.3, 129.6, 128.7, 26.4; MS (EI) m/z 154(M+).
1-(4-(tert-butyl)phenyl)-4-chlorobutan-1-one (10c).10 Prepared from p-tert-butylphenyl magnesium
bromide and 4-chloro butryl chloride as described in general procedure 1. and o-benzoylbenzoyl chloride
as described in general procedure 1. mp.: 47 ºC (46-49 oC)lit, 10a , Yield: 83%; pale yellow solid; IR (KBr,
cm-1): 1684. 1H NMR (CDCl3, 400 MHz); δ 7.92 (d, 2H, J = 8.4 Hz), 7.48 (d, 2H, J = 8.4 Hz), 3.67 (t, 2H,
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J = 6.2 Hz), 3.15 (t, 2H, J = 6.2 Hz), 2.21 (quint, 2H, J = 6.6 Hz), 1.30 (s, 9H); 13C NMR (CDCl3, 75
MHz): δ 198.5, 156.9, 134.1, 127.9, 125.5, 44.6, 35.1, 35.0, 31.2, 26.8; MS (EI) m/z 239 (M++1).
2-Benzoylbenzophenone (11c).11Prepared from phenyl magnesium bromide and o-benzoylbenzoyl
chloride as described in general procedure 1. mp.:139-140 oC (137-139 oC)lit, 11, Yield: 83%; pale yellow
solid; IR (KBr, cm-1): 1672, 1661. 1H NMR (CDCl3, 400 MHz); δ 7.88 (d, J = 7.4 Hz, 4H), 7.79 (s, 4H),
7.69(t, J = 7.1 Hz, 2H), 7.55(t, J = 7.4 Hz, 4H); 13C NMR (CDCl3, 75 MHz): δ 196.5. 139.9, 137.1, 132.9,
130.3, 129.7, 129.6, 128.2; MS (EI) m/z 286 (M+); HRESI-MS (m/z): calculated for
C20H14O2:309.0891(M+Na), found 309.0890 (M+Na).
Benzoylacetonitrile (12c).12 Prepared from phenyl magnesium bromide and cyano acetyl chloride as
described in general procedure 1. mp: 81-83 oC (80-81 oC)lit, 12, Yield: 73%; colourless crystalline solid;
IR (KBr, cm-1): 2263, 1689; 1H NMR (CDCl3, 400 MHz); δ 7.91-7.93 (m, 2H), 7.65-7.69 (m, 1H), 7.51 -
7.55 (m, 2H), 4.10 (s, 2H); 13C NMR (CDCl3, 75 MHz): δ 187, 134.7, 134.2, 129.1, 128.4, 113.7, 29.3;
HRESI-MS (m/z): calculated for C9H7NO(M+Na): 168.0425, found 168.0427 (M+Na).
Compound 13c.13 Prepared from p-chlorophenyl magnesium bromide and methyl-2-(chlorocarbonyl)
benzoate as described in general procedure 1. mp: 108-110 oC (101-102 oC)lit, 10a, Yield: 86%; Colourless
solid; IR (KBr, cm-1): 1727, 1673, 1H NMR (CDCl3, 400 MHz); δ 7.30 - 8.00 (m, 8H), 3.6 (s, 3H); 13C
NMR (CDCl3, 75 MHz): δ 195.5, 194.9, 165.8, 140.9, 139.1, 135.2, 132.2, 130.2, 129.8, 129.4, 128.5,
127.2, 51.9; MS (EI) m/z 274 (M+).
2-Acetyl pyridine (14c).12, 14 Prepared from 2-pyridyl magnesium bromide and acetyl chloride as
described in general procedure 2. Yield: 79 %; colorless liquid; IR (Neat, cm-1): 1699, 1584, 1H NMR
(CDCl3, 400 MHz): δ 8.69 (br, d, 1H), 8.04 (br, d, 1H), 7.82-7.86 (m, 1H), 7.46 - 7.49 (m, 1H), 2.74 (s,
3H); 13C NMR (CDCl3, 75 MHz): δ 199.3, 152.9, 148.4, 136.3, 126.6, 121, 25.1; MS (EI) m/z 121(M+);
HRESI-MS (m/z): calculated for C7H7NO: 144.0425(M+Na), found 144.0423 (M+Na).
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4-chloro-1-(thiophen-2-yl)butan-1-one (15c).15 Prepared from 2-thiophenyl magnesium bromide and
4-chlorobutyryl chloride as described in general procedure 2. Yield: 89 %; colorless liquid; IR (Neat, cm-
1): 1666, 1H NMR (CDCl3, 400 MHz): δ 7.75 (dd, 1H, J =3.7 and 0.8 Hz ), 7.64 (dd, 1H, J = 5 and 0.8
Hz ), 7.13 (dd, 1H, J = 4 .8 and 3.9 Hz ), 3.66 (t, 2H, J = 6.2 Hz), 3.12 (t, 2H, J = ), 2.22 (m, 2H); 13C
NMR (CDCl3, 75 MHz): δ 191.8, 143.9, 133.6, 131.9, 128.1, 44.4,35.9, 26.91; MS (EI) m/z 121(M+);
HRESI-MS (m/z): calculated for C8H10ClOS: 189.0141(M+H), found 189.0141(M+H).
Propiophenone (16c). 16 Colorless liquid; Yield - 54%; IR (Neat, cm-1): 1687; 1H NMR (CDCl3, 400
MHz): δ 7.96 (d, J = 7.6 Hz, 2H), 7.56-7.53(m, 1H), 7.47-7.43(m, 2H), 3.00(q, J = 7.2 Hz, 2H), 1.22(t,
J=7.2 Hz, 3H); 13C NMR (CDCl3, 100 MHz): δ 200.81, 136.85, 132.83, 128.49, 127.91, 31.72, 8.18;
HRESI-MS (m/z): Calculated for C9H10O (M + Na): 157.0629, found (M + Na): 157.0630
Butyrophenone (17c).16 Colorless liquid; Yield - 55%; IR (Neat, cm-1): 1686; 1H NMR (CDCl3, 400
MHz): δ 7.95(d, J = 7.7 Hz), 7.56-7.52 (m, 1H), 7.46-7.43 (m, 2H), 2.94(t, J = 7.2 Hz, 2H), 1.79-1.74 (m,
2H), 1.00(t, J =7.4 Hz, 3H), 13C NMR (CDCl3, 100 MHz): δ 136.99, 132.79, 128.45, 127.94, 40.41,
17.67, 13.80; HRESI-MS (m/z): Calculated for C10H12O (M + Na): 171.0786, found (M + Na): 171.0788
1-Chloroheptan-4-one (18c).17 1-chloroheptan-4-one; Colorless liquid; Yield - 65%; IR (Neat, cm-1):
1741; 1H NMR (CDCl3, 400 MHz): δ 3.58(t, J = 6.2 Hz, 2H), 2.60 (t, J = 7 Hz, 2H), 2.40 (t, J = 7.3 Hz,
2H), 1.64-1.58(m, 2H), 0.92(t, J = 7.4 Hz, 3H); 13C NMR (CDCl3, 100 MHz): δ 209.92, 44.86, 44.51,
39.18, 26.21, 17.27,13.69; HRESI-MS (m/z): Calculated for C7H13ClO (M + H): 149.0733, found (M +
Na): 149.0732.
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1H NMR of 1c
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13C NMR of 1c
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1H NMR of 2c
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13C NMR of 2c
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1H NMR of 3c
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13C NMR of 3c
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1H NMR of 4c
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13C NMR of 4c
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1H NMR of 5c
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13C NMR of 5c
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1H NMR of 6c
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13C NMR of 6c
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1H NMR of 7c
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13C NMR of 7c
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1H NMR of 8c
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13C NMR of 8c
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1H NMR of 9c
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13C NMR of 9c
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1H NMR OF 10c
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13C NMR of 10c
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1H NMR of 11c
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