References and Notes
<A NAME="RG14508ST-1A">1a</A>
Wuts PGM.
Greene TW.
Greene’s Protective Groups in Organic
Synthesis
4th ed.:
Wiley;
Hoboken,
NJ:
2006.
<A NAME="RG14508ST-1B">1b</A>
Kocienski PJ.
Protecting Groups
3rd
ed.:
Georg Thieme Verlag;
Stuttgart:
2004.
For selected examples, see:
<A NAME="RG14508ST-2A">2a</A>
Wu Q.
Fu D.-X.
Hou
A.-J.
Lei G.-Q.
Liu Z.-J.
Chen J.-K.
Zhou T.-S.
Chem. Pharm.
Bull.
2005,
53:
1065
<A NAME="RG14508ST-2B">2b</A>
Adams M.
Pacher T.
Greger H.
Bauer R.
J. Nat. Prod.
2005,
68:
83
<A NAME="RG14508ST-2C">2c</A>
Kanchanapoom T.
Noiarsa P.
Tiengtham P.
Otsuka H.
Ruchirawat S.
Chem.
Pharm. Bull.
2005,
53:
579
<A NAME="RG14508ST-3A">3a</A>
Kawasaki I.
Matsuda K.
Kaneko T.
Bull. Chem. Soc. Jpn.
1971,
44:
1986
<A NAME="RG14508ST-3B">3b</A>
Landini D.
Montanari F.
Rolla F.
Synthesis
1978,
771
<A NAME="RG14508ST-3C">3c</A>
Kamal A.
Gayatri NL.
Tetrahedron Lett.
1996,
37:
3359
<A NAME="RG14508ST-3D">3d</A>
Hwang K.
Park S.
Synth. Commun.
1993,
23:
2845
<A NAME="RG14508ST-4A">4a</A>
Jung ME.
Lyster MA.
J.
Org. Chem.
1977,
42:
3761
<A NAME="RG14508ST-4B">4b</A>
Minamikawa J.
Brossi A.
Tetrahedron Lett.
1978,
3085
<A NAME="RG14508ST-4C">4c</A>
Olah GA.
Narang SC.
Tetrahedron
1982,
38:
2225
<A NAME="RG14508ST-4D">4d</A>
Groutas WC.
Felker D.
Synthesis
1980,
861
<A NAME="RG14508ST-5">5</A>
Morita T.
Okamoto Y.
Sakurai H.
J.
Chem. Soc., Chem. Commun.
1978,
874
<A NAME="RG14508ST-6A">6a</A>
McOmie JFW.
West DE.
Org. Synth., Coll. Vol.
V
Wiley;
New York:
1973.
p.412
<A NAME="RG14508ST-6B">6b</A>
Vickery EH.
Pahler LF.
Eisenbraun EJ.
J. Org. Chem.
1979,
44:
4444
<A NAME="RG14508ST-6C">6c</A>
Demuynck M.
Clercq P.
Vandewalle M.
J.
Org. Chem.
1979,
44:
4863
<A NAME="RG14508ST-6D">6d</A>
Meier H.
Dullweber U.
J. Org. Chem.
1997,
62:
7667
<A NAME="RG14508ST-6E">6e</A>
Ryu I.
Matsubara H.
Yasuda S.
Nakamura H.
Curran D.
J.
Am. Chem. Soc.
2002,
124:
12946
<A NAME="RG14508ST-7A">7a</A>
Williard PG.
Fryhle CB.
Tetrahedron Lett.
1980,
21:
3731
<A NAME="RG14508ST-7B">7b</A>
Konieczny MT.
Maciejewski G.
Konieczny W.
Synthesis
2005,
1575
<A NAME="RG14508ST-8A">8a</A>
Nagaoka H.
Schmid G.
Iio H.
Kishi Y.
Tetrahedron Lett.
1981,
22:
899
<A NAME="RG14508ST-8B">8b</A>
Gerecke M.
Borer R.
Brossi A.
Helv.
Chim. Acta
1976,
59:
2551
<A NAME="RG14508ST-9A">9a</A>
Lansinger JM.
Ronald RC.
Synth. Commun.
1979,
9:
341
<A NAME="RG14508ST-9B">9b</A>
Narayana C.
Padmanabhan S.
Kabalka GW.
Tetrahedron
Lett.
1990,
21:
6977
<A NAME="RG14508ST-10A">10a</A>
Grieco PA.
Ferrino S.
Vidari G.
J. Am. Chem. Soc.
1980,
102:
7586
<A NAME="RG14508ST-10B">10b</A>
Node M.
Hori H.
Fujita E.
J.
Chem. Soc., Perkin. Trans. 1
1976,
2237
<A NAME="RG14508ST-11A">11a</A>
Parker KA.
Petraitis JJ.
Tetrahedron Lett.
1981,
22:
397
<A NAME="RG14508ST-11B">11b</A>
Li T.-T.
Wu YL.
J. Am. Chem. Soc.
1981,
103:
7007
<A NAME="RG14508ST-11C">11c</A>
Kawamura Y.
Takatsuki H.
Torii F.
Horie T.
Bull. Chem. Soc. Jpn.
1994,
67:
511
<A NAME="RG14508ST-12">12</A>
Horie T.
Kobayashi T.
Kawamura Y.
Yoshida I.
Tominaga H.
Yamashita K.
Bull. Chem. Soc. Jpn.
1995,
68:
2033
<A NAME="RG14508ST-13A">13a</A>
Fürstner A.
Seidel G.
J.
Org. Chem.
1997,
62:
2332
<A NAME="RG14508ST-13B">13b</A>
Köster R.
Seidel G.
Organometallic
Syntheses
1988,
4:
440
<A NAME="RG14508ST-13C">13c</A>
Bhatt MV.
J. Organomet. Chem.
1978,
156:
221
<A NAME="RG14508ST-14">14</A>
Yamaguchi S.
Nedachi M.
Yokoyama H.
Hirai Y.
Tetrahedron Lett.
1999,
40:
7363
<A NAME="RG14508ST-15A">15a</A>
Feutrill GI.
Mirrington RN.
Tetrahedron Lett.
1970,
1327
<A NAME="RG14508ST-15B">15b</A>
Feutrill GI.
Mirrington RN.
Aust.
J. Chem.
1972,
25:
1719
<A NAME="RG14508ST-15C">15c</A>
Dodge JA.
Stocksdale MG.
Fahey KJ.
Jones CD.
J.
Org. Chem.
1995,
60:
739
<A NAME="RG14508ST-15D">15d</A>
Smith ABIII.
Schow SR.
Bloom JD.
Thompson AS.
Winzenberg KN.
J.
Am. Chem. Soc.
1982,
104:
4015
<A NAME="RG14508ST-15E">15e</A>
Myers AG.
Tom NJ.
Fraley ME.
Cohen SB.
Mader DJ.
J. Am. Chem. Soc.
1997,
119:
6072
<A NAME="RG14508ST-16">16</A>
Huffman JW.
Joyner H.
Lee MD.
Jordan D.
Pennington WT.
J.
Org. Chem.
1991,
56:
2081
<A NAME="RG14508ST-17">17</A>
Ahmad R.
Saá JM.
Cava MP.
J. Org. Chem.
1977,
42:
1228
<A NAME="RG14508ST-18">18</A>
Hansson C.
Wickberg B.
Synthesis
1976,
191
<A NAME="RG14508ST-19">19</A>
Bernard AM.
Ghiani MR.
Piras PP.
Rivoldini A.
Synthesis
1989,
287
<A NAME="RG14508ST-20A">20a</A>
Mechoulam R.
Gaoni Y.
J.
Am. Chem. Soc.
1965,
87:
3273
<A NAME="RG14508ST-20B">20b</A>
Alonso E.
Ramon DJ.
Yus M.
J.
Org. Chem.
1997,
62:
417
<A NAME="RG14508ST-20C">20c</A>
Wilds AL.
McCormack WB.
J.
Am. Chem. Soc.
1948,
70:
4127
<A NAME="RG14508ST-21">21</A>
Kirschke K.
Wollf E.
J. Prakt. Chem./Chem.-Ztg.
1995,
337:
405
<A NAME="RG14508ST-22">22</A>
Harrison IT.
J.
Chem. Soc., Chem. Commun.
1969,
616
<A NAME="RG14508ST-23">23</A>
McCarthy JR.
Moore JL.
Crege RJ.
Tetrahedron
Lett.
1978,
5183
<A NAME="RG14508ST-24">24</A>
Ireland RE.
Walba D.
Org. Synth.
Coll. Vol. VI:
Wiley;
New
York:
1988.
p.567
<A NAME="RG14508ST-25A">25a</A>
Newman MS.
Sankaran V.
Olson DR.
J. Am. Chem. Soc.
1976,
98:
3237
<A NAME="RG14508ST-25B">25b</A>
Newman MS.
Sankaran V.
Olson DR.
J. Am. Chem. Soc.
1976,
98:
3237
<A NAME="RG14508ST-26">26</A>
Kelly TR.
Dali HM.
Tsang WG.
Tetrahedron
Lett.
1977,
3859
<A NAME="RG14508ST-27">27</A>
Welch SC.
Rao ASCP.
Tetrahedron
Lett.
1977,
505
<A NAME="RG14508ST-28">28</A>
Hwu JR.
Tsay S.-C.
J. Org. Chem.
1990,
55:
5987
<A NAME="RG14508ST-29A">29a</A>
Driver G.
Johnson KE.
Green
Chem.
2003,
5:
163
<A NAME="RG14508ST-29B">29b</A>
Chauhan SMS.
Jain N.
J.
Chem. Res.
2004,
693
<A NAME="RG14508ST-30A">30a</A>
Melillo DG.
Larsen RD.
Mathre DJ.
Shukis WF.
Wood AW.
Collelouri JR.
J. Org. Chem.
1987,
52:
5143
<A NAME="RG14508ST-30B">30b</A>
Fujii N.
Irie H.
Yajima H.
J.
Chem. Soc., Perkin Trans. 1
1977,
2288
<A NAME="RG14508ST-31A">31a</A>
Boger DL.
Miyazaki S.
Kim SH.
Wu JH.
Castle SL.
Loiseleur O.
Jin Q.
J. Am. Chem. Soc.
1999,
121:
10004
<A NAME="RG14508ST-31B">31b</A>
Boger DL.
Kim SH.
Mori Y.
Weng J.-H.
Rogel O.
Castle SL.
McAtee JJ.
J. Am. Chem. Soc.
2001,
123:
1862
<A NAME="RG14508ST-31C">31c</A>
Node M.
Nishide K.
Fuji K.
Fujita E.
J. Org. Chem.
1980,
45:
4275
<A NAME="RG14508ST-32">32</A>
Evans DA.
Dinsmore CJ.
Ratz AM.
Evrard DA.
Barrow JC.
J. Am. Chem. Soc.
1997,
119:
3417
<A NAME="RG14508ST-33">33</A>
Inaba T.
Umezawa I.
Yuasa M.
Inoue T.
Mihashi S.
Itokawa H.
Ogura K.
J.
Org. Chem.
1987,
52:
2957
<A NAME="RG14508ST-34">34</A> For a review, see:
Schmalz H.-G.
Gotov B.
Böttcher A.
In Arene Metal Complexes.
Topics in Organometallic Chemistry
Vol. 7:
Kündig EP.
Springer;
Berlin:
2004.
p.157
<A NAME="RG14508ST-35A">35a</A>
Geller T.
PhD Dissertation
TU-Berlin;
Germany:
1998.
<A NAME="RG14508ST-35B">35b</A>
Majdalani A.
Schmalz H.-G.
Synlett
1997,
1303
<A NAME="RG14508ST-35C">35c</A>
Majdalani A.
Schmalz H.-G.
Tetrahedron Lett.
1997,
38:
4545
<A NAME="RG14508ST-35D">35d</A>
Geller T.
Schmalz H.-G.
Bats JW.
Tetrahedron
Lett.
1998,
39:
1537
<A NAME="RG14508ST-35E">35e</A>
Dehmel F.
Schmalz H.-G.
Org. Lett.
2001,
3:
3579
<A NAME="RG14508ST-35F">35f</A>
Dehmel F.
Lex J.
Schmalz H.-G.
Org.
Lett.
2002,
4:
3915
<A NAME="RG14508ST-36">36</A> For an efficient entry to stilbene 5 by cross-metathesis, see:
Velder J.
Ritter S.
Lex J.
Schmalz H.-G.
Synthesis
2006,
273
<A NAME="RG14508ST-37A">37a</A>
Polunin KE.
Polunina IA.
Schmalz H.-G.
Mendeleev
Commun.
2002,
12:
178
<A NAME="RG14508ST-37B">37b</A>
Polunin KE.
Schmalz H.-G.
Russ.
J. Coord. Chem.
2004,
30:
252
<A NAME="RG14508ST-38A">38a</A> For
synthetic approaches towards pestatone, see:
Cueto M.
Jensen PR.
Kaufmann C.
Fenical W.
Lobkovsky E.
Clardy J.
J. Nat. Prod.
2001,
64:
1444
<A NAME="RG14508ST-38B">38b</A>
Kaiser F.
Schmalz H.-G.
Tetrahedron
2003,
59:
7345
<A NAME="RG14508ST-38C">38c</A>
Iijima D.
Tanaka D.
Hamada M.
Ogamino T.
Ishikawa Y.
Nishiyama S.
Tetrahedron Lett.
2004,
45:
5469
For a review on colchicine total
synthesis, see:
<A NAME="RG14508ST-39A">39a</A>
Graening T.
Schmalz H.-G.
Angew. Chem. Int. Ed.
2003,
42:
2580 ; Angew. Chem. 2003, 115, 2684
<A NAME="RG14508ST-39B">39b</A> For a recent work from
this laboratory, see:
Graening T.
Bette V.
Neudörfl J.
Lex J.
Schmalz H.-G.
Org.
Lett.
2005,
7:
4317
For previous examples of selective O-demethylation reactions with thiolate-based
reagents which, however, require harsh reaction conditions, long
reaction times and/or the use of HMPT as a toxic additive,
see:
<A NAME="RG14508ST-40A">40a</A>
Moos WH.
Gless RD.
Rapoport H.
J. Org. Chem.
1982,
47:
1831
<A NAME="RG14508ST-40B">40b</A>
Lal K.
Zarate EA.
Youngs WJ.
Salomon RG.
J.
Am. Chem. Soc.
1986,
108:
1311
<A NAME="RG14508ST-40C">40c</A>
Dodge JA.
Stocksdale MG.
Fahey KJ.
Jones CD.
J.
Org. Chem.
1995,
60:
739
<A NAME="RG14508ST-40D">40d</A>
Loubinoux B.
Coudert G.
Guillaumet G.
Synthesis
1980,
638
<A NAME="RG14508ST-40E">40e</A>
Lal K.
Ghosh S.
Salomon RG.
J.
Org. Chem.
1987,
52:
1072
<A NAME="RG14508ST-41A">41a</A>
Kappe CO.
Stadler A.
Microwaves in Organic and Medicinal Chemistry
Wiley-VCH;
Weinheim:
2005.
<A NAME="RG14508ST-41B">41b</A>
Kappe CO.
Angew. Chem. Int. Ed.
2004,
43:
6250
<A NAME="RG14508ST-41C">41c</A>
Kappe CO.
Dallinger D.
Nat. Rev.
Drug Discovery
2006,
5:
51
For the use of microwave irradiation
in the cleavage or trans protection of
aryl methyl ether using different reagents, see:
<A NAME="RG14508ST-42A">42a</A>
Fredriksson A.
Stone-Elander S.
J. Labelled Compd. Radiopharm.
2002,
45:
529
<A NAME="RG14508ST-42B">42b</A>
Marette C.
Larrouquet C.
Tisne’s P.
Deloyeb J.-B.
Grasa E.
Tetrahedron
Lett.
2006,
47:
6947
<A NAME="RG14508ST-43">43</A>
DMF (99.8%, Fluka) was stored
over molecular sieves. GC-MS measurements were carried
out on an Agilent HP6890 instrument with MS detector 5937 N using
an Optima 1 MS (Macherey-Nagel) 30 m × 0.25 mm
capillary column with H2 as carrier gas. NMR data were
measured on Bruker DPX 300 and AC 250 instruments. Chemical shifts
(δ) are given in ppm relative to the solvent reference
as the internal standard. Reactions under microwave irradiation
were performed in a CEM Discover instrument (300 W) in glass tubes
with temperature and pressure control.
Preparation
of the Reagent (LiSEt): In a dry 500-mL Schlenk flask a solution
of n-BuLi (1.3 M) in hexane (120 mL,
160 mmol) was diluted with hexane (150 mL) under an argon atmosphere.
The solution was cooled to 0 ˚C and under rapid stirring
EtSH (200 mmol, 1.25 equiv, 15 mL) was added dropwise, whereupon
a white precipitate formed. The reaction mixture was stirred at
0 ˚C for 10 min and at r.t. for 30 min. After removal of
the solvent (always ensuring inert conditions) the residue was dried
in vacuo to give LiSEt as a white solid (10.6 g, 156 mmol, 97%).
The product was stored under argon at ambient temperature. C2H5SLi;
M = 68.06 g/mol. ¹H NMR (250
MHz, DMSO): δ = 1.06 (t, ³
J = 7.2 Hz, 3 H, H2), 2.27 (q, ³
J = 7.3 Hz, 2 H, H1).
General Procedure: The substrate (0.6 mmol,
1 equiv) and LiSEt (1.2 mmol, 2 equiv) were weighed into the reaction vessel
(either a Schlenk tube or a microwave reactor), which was then evacuated
and flushed with argon three times before DMF (5 mL) was added and
the reaction mixture was heated/irradiated as specified
in Table
[¹]
. Reactions
were monitored by TLC and/or GC-MS. For workup,
the mixture was cooled to r.t. and partitioned between 2 N aq HCl
(5 mL) and MTBE (5 mL). The aqueous layer was re-extracted with MTBE
(3 × 10 mL). The combined organic layers were washed with
brine (20 mL), dried over MgSO4, filtered through a pad
of silica and solvents were evaporated. The residue was flash chromatographed
on silica gel with
c-hexane-EtOAc
(4:1).
3-Methoxyphenol
(10): colorless oil. ¹H
NMR (CDCl3): δ = 3.76 (s, 3 H), 5.03
(br s, 1 H), 6.40-6.43, 6.46-6.50 (m, 3 H), 7.09-7.14
(m, 1 H). ¹³C NMR (CDCl3): δ = 55.3
(q), 101.5, 106.4, 107.9 (3 × d), 130.1 (d), 156.7 (s),
160.9 (s). HRMS (EI, 70 eV): m/z calcd for C7H8O2:
124.0524; found: 124.053.
3-Methoxy-2-methylphenol
(12): white solid; mp 42-43 ˚C. ¹H
NMR (CDCl3): δ = 2.11 (s, 3 H), 3.81
(s, 3 H), 4.80 (s, 1 H), 6.44 (d, ³
J = 8.5 Hz, 1 H), 6.47 (d, ³
J = 8.5 Hz, 1 H), 7.02 (ψt, ³
J = 8.5 Hz, 1 H). ¹³C
NMR (CDCl3): δ = 7.9 (q), 55.6 (q),
103.0 (d), 108.0 (d), 112.1 (s), 126.4 (d), 154.3 (q), 158.6 (q).
HRMS (EI, 70 eV): m/z calcd for C8H10O2: 138.0681;
found: 138.068.
2-Hydroxy-6-methoxybenzonitrile
(14): white solid; mp 163-164 ˚C. ¹H
NMR (CD3OD): δ = 3.87 (s, 3 H), 6.50
(d, ³
J = 8.4
Hz, 1 H), 6.52 (d, ³
J = 8.4
Hz, 1 H), 7.34 (ψt, ³
J = 8.5
Hz, 1 H). ¹³C NMR (CD3OD): δ = 56.7
(q), 90.6 (s), 102.9 (d), 109.0 (d), 115.4 (s), 136.1 (d), 163.0
(s), 163.9 (s). IR (ATR): 3220 (br m), 2230 (s), 1607 (s), 1594
(s), 1476 (s) cm-¹. HRMS (EI, 70 eV): m/z calcd
for C8H7NO2: 149.0477; found: 149.047.
3,5-Dimethoxybenzoic acid
(16):
GC-MS and NMR data matched those of an authentic(commercial)
sample.
1-(4-Hydroxy-3,5-dimethoxyphenyl)ethanone
(20): colorless oil. ¹H
NMR (CDCl3): δ = 2.54 (s, 3 H), 3.92
(s, 6 H), 6.03 (br s, 1 H), 7.22 (s, 2 H). ¹³C
NMR (CDCl3): δ = 26.2 (q), 56.4 (q),
105.7 (d), 128.8 (s), 139.7 (s), 146.7 (s), 200.3 (s). IR (ATR):
3350 (br m), 1728 (s) cm-¹. HRMS:
m/z calcd
for C10H12O4: 196.0736; found:
196.074.
5-Bromo-2,3-dimethoxyphenol
(22a): white solid; mp 68-70 ˚C. ¹H
NMR (CDCl3): δ = 3.82 (s, 3 H), 3.85
(s, 3 H), 5.83 (br s, 1 H), 6.59 (d, 4
J = 2.1
Hz, 1 H), 6.75 (d, 4
J = 2.1
Hz, 1 H). ¹³C NMR (CDCl3): δ = 56.5
(q), 60.9 (q), 107.9 (d), 111.6 (d), 116.4 (s), 134.8 (s), 149.9
(s), 152.8 (s). MS (EI, 70 eV; isotope pattern reflected a molecule
with one bromine atom): m/z (%) = 234 (95) [M]+,
232 (100) [M]+, 219 (95), 217
(97), 191 (46), 189 (55), 173 (29), 171 (31), 110 (14), 67 (41).
HRMS: m/z calcd
for C8H9O3
79Br: 231.9735;
found: 231.974.
4-Bromo-2,6-dimethoxyphenol (22b): white solid; mp 90-92 ˚C. ¹H
NMR (CDCl3): δ = 3.86 (s, 6 H), 5.42
(br s, 1 H), 6.70 (s, 2 H). ¹³C NMR
(CDCl3): δ = 56.4 (q), 108.4 (d), 111.04
(s), 138.9 (s), 147.5 (s). MS (EI, 70 eV; isotope pattern reflected
a molecule with one Br atom): m/z (%) = 234 (93) [M]+,
232 (100) [M]+, 219 (37),
217 (41), 191 (27), 189 (30), 176 (16), 174 (16), 110 (13), 67 (19),
50 (16). HRMS: m/z calcd for C8H9
79BrO3:
231.9735; found: 231.974.
2-Bromo-4,6-dichloro-3-methoxy-5-methylphenol
(24): white solid; mp 128 ˚C. ¹H
NMR (CDCl3): δ = 2.44 (s, 3 H), 3.85
(s, 3 H), 5.91 (s, 1 H). ¹³C NMR (CDCl3): δ = 18.1
(q), 60.6 (q), 103.7 (s), 117.0 (s), 121.2 (s), 134.9 (s), 148.0
(s), 152.5 (s). MS (EI, 70 eV; isotope pattern reflected a molecule
with one Br and two Cl atoms): m/z (%) = 290 (6) [M]+,
288 (44) [M]+, 286 (100) [M]+,
284 (63) [M]+, 273 (14), 271
(31), 269 (20), 245 (23), 243 (56), 241 (34), 179 (15), 177 (14).
HRMS: m/z calcd
for C8H7O2
79Br³5Cl2: 283.9006;
found: 283.901.
