References and Notes
<A NAME="RG35908ST-1A">1a</A>
Budriesi R.
Ioan P.
Locatelli A.
Cosconati S.
Leoni A.
Ugenti MP.
Andreani A.
Di Toro R.
Bedini A.
Spampinato S.
Marinelli L.
Novellino E.
Chiarini A.
J. Med. Chem.
2008,
51:
1592
<A NAME="RG35908ST-1B">1b</A>
Fookes CJR.
Pham TQ.
Mattner F.
Greguric I.
Loc’h C.
Liu X.
Berghofer P.
Shepherd R.
Gregoire M.-C.
Katsifis A.
J.
Med. Chem.
2008,
51:
3700
<A NAME="RG35908ST-1C">1c</A>
Jin Z.
Nat.
Prod. Rep.
2005,
22:
196
<A NAME="RG35908ST-2">2</A>
Rival Y.
Grassy G.
Michel G.
Chem.
Pharm. Bull.
1992,
40:
1170
<A NAME="RG35908ST-3A">3a</A>
Hamdouchi C.
de Blas J.
del Prado M.
Gruber J.
Heinz BA.
Vance L.
J.
Med. Chem.
1999,
42:
50
<A NAME="RG35908ST-3B">3b</A>
Lhassani M.
Chavignon O.
Chezal J.-M.
Teulade
J.-C.
Chapat J.-P.
Snoeck R.
Andrei G.
Balzarini J.
De Clercq E.
Gueiffier A.
J. Med. Chem.
1999,
34:
271
<A NAME="RG35908ST-4A">4a</A>
Fisher MH.
Lusi A.
J.
Med. Chem.
1972,
15:
982
<A NAME="RG35908ST-4B">4b</A>
Rival Y.
Grassy G.
Taudou A.
Ecalle R.
Eur. J. Med. Chem.
1991,
26:
13
<A NAME="RG35908ST-5">5</A>
Rupert KC.
Henry JR.
Dodd JH.
Wadsworth SA.
Cavender DE.
Olini GC.
Fahmy B.
Siekierka JJ.
Bioorg.
Med. Chem. Lett.
2003,
13:
347
<A NAME="RG35908ST-6">6</A>
Hamdouchi C.
Zhong B.
Mendoza J.
Collins E.
Jaramillo C.
De Diego JE.
Robertson D.
Spencer
CD.
Anderson BD.
Watkins SA.
Zhang F.
Brooks HB.
Bioorg. Med. Chem. Lett.
2005,
15:
1943
<A NAME="RG35908ST-7">7</A>
Goodacre SC.
Street LJ.
Hallett DJ.
Crawforth JM.
Kelly S.
Owens AP.
Blackaby WP.
Lewis RT.
Stanley J.
Smith AJ.
Ferris P.
Sohal B.
Cook SM.
Pike A.
Brown N.
Wafford KA.
Marshall G.
Castro
JL.
Atack JR.
J. Med. Chem.
2006,
49:
35
<A NAME="RG35908ST-8">8</A>
Abe Y.
Kayakiri H.
Satoh S.
Inoue T.
Sawada Y.
Imai K.
Inamura N.
Asano M.
Hatori C.
Katayama A.
Oku T.
Tanaka H.
J. Med. Chem.
1998,
41:
564
<A NAME="RG35908ST-9">9</A>
Sanfilippo PJ.
Urbanski M.
Press JB.
Dubinsky B.
Moore JB.
J.
Med. Chem.
1988,
31:
2221
<A NAME="RG35908ST-10A">10a</A>
Koubachi J.
El Kazzouli S.
Berteina-Raboin S.
Mouaddib A.
Guillaumet G.
J. Org. Chem.
2007,
72:
7650
<A NAME="RG35908ST-10B">10b</A>
Imaeda Y.
Kawamoto T.
Tobisu M.
Konishi N.
Hiroe K.
Kawamura M.
Tanaka T.
Kubo K.
Bioorg. Med. Chem.
2008,
16:
3125
<A NAME="RG35908ST-11">11</A>
Katritzky AR.
Xu Y.-J.
Tu H.
J.
Org. Chem.
2003,
68:
4935
<A NAME="RG35908ST-12A">12a</A>
Bienayme H.
Bouzid K.
Angew.
Chem. Int. Ed.
1998,
37:
2234
<A NAME="RG35908ST-12B">12b</A>
Blackburn C.
Guan B.
Fleming P.
Shiosaki K.
Tsai S.
Tetrahedron
Lett.
1998,
39:
3635
<A NAME="RG35908ST-12C">12c</A>
Groebke K.
Weber L.
Mehlin F.
Synlett
1998,
661
<A NAME="RG35908ST-12D">12d</A>
DiMauro EF.
Kennedy JM.
J.
Org. Chem.
2007,
72:
1013
<A NAME="RG35908ST-12E">12e</A>
Parchinsky VZ.
Shuvalova O.
Ushakova O.
Kravchenko DV.
Krasavin M.
Tetrahedron Lett.
2006,
47:
947
<A NAME="RG35908ST-12F">12f</A>
Mandair GS.
Light M.
Russell A.
Hursthouse M.
Bradley M.
Tetrahedron Lett.
2002,
43:
4267
<A NAME="RG35908ST-12G">12g</A>
Rousseau AL.
Matlaba P.
Parkinson CJ.
Tetrahedron Lett.
2007,
48:
4079
<A NAME="RG35908ST-12H">12h</A>
Ireland SM.
Tye H.
Whittaker M.
Tetrahedron Lett.
2003,
44:
4369
<A NAME="RG35908ST-12I">12i</A>
Varma RS.
Kumar D.
Tetrahedron
Lett.
1999,
40:
7665
<A NAME="RG35908ST-12J">12j</A>
Chen JJ.
Golebiowski A.
McClenaghan J.
Klopfenstein SR.
West L.
Tetrahedron Lett.
2001,
42:
2269
<A NAME="RG35908ST-12K">12k</A>
Blackburn C.
Tetrahedron
Lett.
1998,
39:
5469
<A NAME="RG35908ST-13">13</A>
Parenty ADC.
Song Y.-F.
Richmond CJ.
Cronin L.
Org.
Lett.
2007,
9:
2253
<A NAME="RG35908ST-14">14</A>
Bakherad M.
Nasr-Isfahani H.
Keivanloo A.
Doostmohammadi N.
Tetrahedron Lett.
2008,
49:
3819
<A NAME="RG35908ST-15">15</A>
Dömling A.
Chem.
Rev.
2006,
106:
17
For greener use of PEG-400 as solvent,
see:
<A NAME="RG35908ST-16A">16a</A>
Han W.
Liu C.
Jin Z.-L.
Org.
Lett.
2007,
9:
4005
<A NAME="RG35908ST-16B">16b</A>
Kouznetsov VV.
Merchan Arenas DR.
Romero Bohórquez AR.
Tetrahedron
Lett.
2008,
49:
3097 ;
and references cited therein
<A NAME="RG35908ST-17A">17a</A> For
significant use of ZrCl4, see: Review paper:
Smitha G.
Chandrasekhar S.
Reddy CS.
Synthesis
2008,
829
<A NAME="RG35908ST-17B">17b</A>
Bhagat S.
Chakraborti AK.
J. Org. Chem.
2008,
73:
6029
<A NAME="RG35908ST-17C">17c</A>
Chakraborti AK.
Kondaskar A.
Tetrahedron Lett.
2003,
44:
8315
<A NAME="RG35908ST-18">18</A>
Representative
Experimental Procedure for the Synthesis of N
-
tert
-Butyl-2-(4-chlorophenyl)imidazo[1,2-
a
]pyridin-3-amine
(Table 2, entry 1): To a mixture of 2-aminopyridine (0.19 g,
2 mmol) and 4-chlorobenzaldehyde (0.28 g, 2 mmol) in PEG-400 (2
mL), tert-butyl isocyanide (0.17 g, 2
mmol) and ZrCl4 (47 mg, 10 mol%) were added. The
mixture was allowed to stir at 50 ˚C under open air. After
completion of the reaction (4.5 h, monitored by TLC), the resulting
mixture was extracted with EtOAc and washed with H2O.
The organic layer was dried over anhyd Na2SO4, filtered
and concentrated under reduced pressure. The column chromatographic
purification of crude product over silica gel (mesh size: 60-120)
eluting with EtOAc-hexane (1:1.5) afforded N-tert-butyl-2-(4-chlorophenyl)imidazo-[1,2-a]pyridin-3-amine (0.48 g, 85%);
white solid; mp 146-149 ˚C. MS (ESI): m/z = 300 [M + 1]. ¹H
NMR (400 MHz, CDCl3): δ = 1.06 (s,
9 H), 3.00 (br, NH), 6.78 (t, J = 6.8
Hz, 1 H), 7.15 (t, J = 8.0 Hz,
1 H), 7.40 (d, J = 8.8 Hz, 2
H), 7.54 (d, J = 7.2 Hz, 1 H),
7.92 (d, J = 8.8 Hz, 1 H), 8.20
(d, J = 6.8 Hz, 1 H). ¹³C
NMR (100 MHz, CDCl3): δ = 30.3 (3 × Me), 56.4
(C), 111.5 (CH), 117.3 (CH), 123.3 (CH), 123.4 (C), 124.3 (CH),
128.4 (2 × CH), 129.3 (2 × CH), 133.1 (C), 133.7
(C), 138.3 (C), 142.0 (C). IR (KBr): 3457, 2972, 1635, 1194, 770
cm-¹. Anal. Calcd for C17H18ClN3:
C, 68.11; H, 6.05; N, 14.02. Found: C, 67.89; H, 6.07; N, 13.99.
All
reactions (Tables
[¹]
-
[³]
) were carried out following
this procedure.
<A NAME="RG35908ST-19">19</A>
Lyon MA.
Kercher TS.
Org. Lett.
2004,
6:
4989
<A NAME="RG35908ST-20">20</A>
Blackburn C.
Guan B.
Tetrahedron Lett.
2000,
41:
1495
