References and Notes
1 For a recent review, see: Brummond KM.
Loyer-Drew JA.
C-C Bond Formation (Part 1) by Addition Reactions: Alder-Ene
Reaction, In Comprehensive Organometallic Chemistry
III
Vol. 10:
Crabtree RH.
Mingos MP.
Ojima I.
Elsevier;
Oxford:
2007.
Chap.
10.12.
2a
Brummond KM.
Chen H.
Sill P.
You L.
J.
Am. Chem. Soc.
2002,
124:
15186
2b
Brummond KM.
Mitasev B.
Org. Lett.
2004,
6:
2245
2c Subsequently a similar
finding was reported: Shibata T.
Takesue Y.
Kadowaki S.
Takagi K.
Synlett
2003,
268
For example, see:
3a
Brummond KM.
You L.
Tetrahedron
2005,
61:
6180
3b
Mitasev B.
Yan B.
Brummond KM.
Heterocycles
2006,
70:
367 ; and references cited therein
For an enamide cycloisomerization,
see:
4a
Trost BM.
Pedregal C.
J. Am.
Chem. Soc.
1992,
114:
7292
4b
Arisawa M.
Terada Y.
Theeraladanon C.
Takahashi K.
Nakagawa M.
Nishida A.
J. Organomet. Chem.
2005,
690:
5398
For preparation of cyclic enamides
and natural products containing cyclic enamides, see:
5a
Kinderman SS.
Maarseveen JHV.
Schoemaker HE.
Hiemstra H.
Rutjes FPJT.
Org.
Lett.
2001,
3:
2045
5b
Klapars A.
Campos KR.
Chen C.-Y.
Volante RP.
Org. Lett.
2005,
7:
1185
5c
Zhang X.
Zhang Y.
Huang J.
Hsung RP.
Kurtz KCM.
Oppenheimer J.
Petersen ME.
Sagamanova IK.
Shen L.
Tracey MR.
J. Org. Chem.
2006,
71:
4170
5d
Toumi M.
Couty F.
Evano G.
Angew. Chem
Int. Ed.
2007,
46:
572
5e
Yet L.
Chem.
Rev.
2003,
103:
4283 ;
and references cited therein
6 For an example, see: Zhang W.
Zhang X.
Angew. Chem. Int.
Ed.
2006,
45:
5515
7
O’Donnell MJ.
Plot RL.
J.
Org. Chem.
1982,
47:
2663
8
Ni Y.
Amarasinghe KKD.
Ksebati B.
Montgomery J.
Org. Lett.
2003,
5:
3771
9a
Garner P.
Park JM.
J.
Org. Chem.
1987,
52:
2361
9b
Koskinen AMP.
Otsomaa LA.
Tetrahedron
1997,
53:
6473
9c
Roush WR.
Hunt JA.
J.
Org. Chem.
1995,
60:
798
10a
Seyferth D.
Marbor RS.
Hilbert P.
J. Org. Chem.
1971,
36:
1379
10b
Ohira S.
Synth.
Commun.
1989,
19:
561
11a
Crisp GT.
Jiang Y.-L.
Pullman PJ.
Savi CD.
Tetrahedron
1997,
53:
17489
11b
Meffre P.
Gauzy L.
Branquet E.
Durand P.
Goffic FL.
Tetrahedron
1996,
52:
11215
11c
Meffre P.
Gauzy L.
Perdigues C.
Desanges-Levecque F.
Branquet E.
Durand P.
Goffic FL.
Tetrahedron
Lett.
1995,
36:
877
12
Trost BM.
Stiles DT.
Org. Lett.
2005,
7:
2117
13
Shen L.
Hsung RP.
Zhang Y.
Antoline JE.
Zhang X.
Org.
Lett.
2005,
7:
3081
14 For a recent review, see: Wei L.-L.
Xiong H.
Hsung RP.
Acc. Chem. Res.
2003,
36:
773 ; and references cited therein
15
General Procedure
for the Copper-Catalyzed Coupling Protocol to Prepare an Allenamide - Preparation
of 3-(3-Methylbuta-1,2-dienyl)-4-(pent-2-ynyl)oxazolidin-2-one
(1b)
A flame-dried 25 mL round-bottom
flask was charged with oxazolidinone 8b (0.321
g, 2.10 mmol), copper(I) thiophene-2-carboxylate (CuTC, 0.040 g,
0.21 mmol), BaO (0.643 g, 4.20 mmol), and Cs2CO3 (1.367
g, 4.20 mmol). After flushing with nitrogen, toluene (15 mL) was
added, followed by DMEDA (45 µL, 0.42 mmol), then 1-iodo-3-methylbuta-1,2-diene
(500 µL, 4.20 mmol). The flask was covered with aluminum
foil and heated at 50 ˚C for 20 h. The reaction
was then cooled to r.t., filtered through a short pad of Celite,
and concentrated in vacuo. The residue was purified by column chromatography [SiO2,
eluting with 95% to hexanes-EtOAc (1:1), 5% Et3N] to
afford the allenamide 1b (0.363 g, 79%)
as a pale yellow oil.
¹H NMR (300 MHz,
CDCl3): δ = 6.57 (sept, J = 2.6 Hz,
1 H), 4.43 (app t, J = 8.7
Hz, 1 H), 4.32 (dd, J = 8.8,
4.3 Hz, 1 H), 3.97-3.90 (m, 1 H), 2.54-2.47 (m,
2 H), 2.20-2.11 (m, 2 H), 1.83 (d, J = 2.6
Hz, 3 H), 1.80 (d, J = 2.6
Hz, 3 H), 1.12 (t, J = 7.5
Hz, 3 H). ¹³C NMR (75 MHz, CDCl3): δ = 191.5, 155.5,
108.9, 93.0, 85.3, 72.8, 67.1, 53.8, 22.3, 22.0, 21.8, 14.2, 12.5.
IR (neat): 1968, 1757 cm-¹. MS: m/z (%) = 220 (10),
219 (50), 204 (31), 190 (68), 152 (88), 108 (87), 81 (100), 67 (92).
HRMS (EI): m/z calcd for C13H17NO2 [M+]: 219.1259;
found: 219.1259.
16
General Procedure
for the Alder-ene Reaction - Preparation of (7
Z
)-7-Ethylidene-7,7a-dihydro-6-(prop-1-en-2-yl)pyrrolo[1,2-
c
]oxazol-3(1
H
)-one (15b)
To a flame-dried test tube
equipped with a magnetic stirring bar was added allenamide 14b (0.022 g, 0.12 mmol). The test tube
was evacuated and charged with nitrogen (3×). Then, toluene
(4.4 mL) was added followed by addition of [Rh(CO)2Cl]2 (0.002
g, 0.01 mmol). The reaction mixture was stirred at r.t. for 3.5
h and upon completion, the light yellow-brown solution was chromatographed [SiO2, hexanes-EtOAc
(4:1)] to give the desired cross-conjugated triene 15b (0.016 g, 72% yield). ¹H
NMR (300 MHz, CDCl3): δ = 6.67 (s,
1 H), 5.76 (qd, J = 7.2,
3.1 Hz, 1 H), 5.21-5.11 (m, 3 H), 4.84 (app t, J = 8.5 Hz,
1 H), 4.24 (app t, J = 8.7
Hz, 1 H), 1.93 (s, 3 H), 1.68 (dd, J = 7.1,
1.8 Hz, 3 H). ¹³C NMR (75 MHz, CDCl3): δ = 157.4,
140.1, 135.8, 130.3 130.0, 116.5, 115.0, 70.7, 61.6, 23.3, 16.0.
IR (neat): 1772 cm-¹. MS: m/z (%) = 191
(30), 146 (46), 132 (61), 117 (47), 91 (36), 86 (64), 84 (100).
HRMS (EI): m/z calcd for C11H13NO2 [M+]:
191.0946; found: 191.0952.
17
(
Z
)-7,8,9,9a-Tetrahydro-7-methylene-6-vinyl-oxazolo[3,4-
a
]azepin-3-(1
H
)-one (17a)
Following the general procedure
for the Alder-ene reaction, 17a was obtained
in 12% yield. ¹H NMR (300 MHz, CDCl3): δ = 6.62
(s, 1 H), 6.32 (dd, J = 17.1,
10.6 Hz, 1 H), 5.33 (dd, J = 17.1,
1.4 Hz, 1 H), 5.24 (br s, 1 H), 5.06 (dd, J = 10.6,
1.4 Hz, 1 H), 5.06 (s, 1 H), 5.05 (s, 1 H), 4.50 (app t, J = 8.4 Hz, 1
H), 4.20-4.10 (m, 1 H), 3.94 (app t, J = 8.4
Hz, 1 H), 2.71-2.65 (m, 1 H), 2.38-2.29 (m, 1
H), 2.16-2.08 (m, 1 H), 1.88-1.77 (m, 1 H). ¹³C
NMR (75 MHz, CDCl3): δ = 156.4, 142.0, 136.5,
126.3, 123.7, 117.9, 114.4, 68.4, 56.9, 35.1, 34.1. IR (neat): 1755,
1640 cm-¹. MS: m/z (%) = 191
(87), 176 (46), 158 (54), 157 (30), 129 (45), 105 (100), 104 (42).
HRMS (EI): m/z calcd for C11H13NO2 [M+]:
191.0946; found: 191.0947.
18
General Procedure
for the Pauson-Khand Reaction - Preparation of
Enone 18a
To a flame-dried test tube equipped with
a magnetic stirring bar was added allenamide 16d (0.009
g, 0.04 mmol). The test tube was evacuated and charged with carbon
monoxide (3×), then toluene (5.2 mL) was added followed
by [Rh(CO)2Cl]2 (0.002 g,
0.004 mmol). The reaction mixture was heated at 85 ˚C
for 1 h. Upon completion of the reaction (TLC), the mixture was
cooled to r.t. and chromatographed [SiO2, hexanes-EtOAc
(1:1)] to give 18a as an oil (dr,
3:1, 0.008 g, 75% yield).
Major diastereomer: ¹H
NMR (300 MHz, CDCl3): δ = 6.68 (s,
1 H), 4.60 (app t, J = 8.3
Hz, 1 H), 4.19-4.09 (m, 1 H), 3.96 (dd, J = 10.0,
8.5 Hz, 1 H), 3.25 (dt, J = 18.4,
3.2 Hz, 1 H), 2.86-2.76 (m, 2 H), 2.61 (ddd, J = 17.1,
12.8, 3.5 Hz, 1 H), 2.09 (dt, J = 14.1,
4.0 Hz, 1 H), 2.00-1.86 (m, 1 H), 1.24 (d, J = 7.2 Hz,
6 H), 1.20 (d, J = 6.9
Hz, 3 H). ¹³C NMR (75 MHz, CDCl3): δ = 206.6,
159.8, 155.2, 146.5, 123.0, 117.8, 67.6, 58.6, 44.6, 29.2, 28.4,
25.7, 20.3, 20.1, 16.0. IR (neat): 1760, 1682, 1651 cm-¹.
MS: m/z (%) = 261
(62), 246 (100), 232 (16), 218 (47), 174 (6). HRMS (EI): m/z calcd for C15H19NO3 [M+]:
261.1365; found: 261.1361.
19
Xiong H.
Hsung RP.
Wei L.-L.
Berry CR.
Mulder JA.
Stockwell B.
Org. Lett.
2000,
2:
2869
20
Diels-Alder
Reaction - Preparation of Tetracyclic Compound 19
To
a solution of triene 2b (0.006 g, 0.03
mmol) in toluene (0.5 mL) was added N-phenylmaleimide
(0.005 g, 0.03 mmol). The reaction mixture was heated at 75 ˚C
for 5 h then, after cooling to r.t. was chromatographed [SiO2, hexanes-EtOAc,
(1:1)] to give the product 19 as
a white solid (0.008 g, 75% yield). ¹H
NMR (300 MHz, CDCl3): δ = 7.46-7.34
(m, 3 H), 7.11-7.08 (m, 2 H), 5.49 (t, J = 7.5
Hz, 1 H), 4.60 (dd, J = 9.0,
5.8 Hz, 1 H), 4.40 (t, J = 7.4
Hz, 1 H), 4.35-4.34 (m, 1 H), 4.11 (dd, J = 11.5,
7.8 Hz, 1 H), 3.95-3.84 (m, 1 H), 3.27 (ddd, J = 8.9, 7.1,
1.7 Hz, 1 H), 2.77 (dd, J = 14.5,
1.7 Hz, 1 H), 2.69 (dd, J = 12.7,
3.2 Hz, 1 H), 2.40-2.32 (m, 1 H), 2.17-2.07 (m,
2 H), 2.02 (s, 3 H), 1.87 (t, J = 12.3
Hz, 1 H), 1.00 (t, J = 7.5
Hz, 3 H). ¹³C NMR (75 MHz, CD2Cl2): δ = 178.5,
176.7, 157.4, 134.8, 132.5, 130.4, 130.2, 129.3, 128.9, 128.6, 127.1,
69.6, 57.0, 52.8, 40.1, 39.3, 32.3, 28.9, 22.6, 21.7, 14.3. IR (neat):
1746, 1706 cm-¹. MS: m/z (%) = 393
(40), 392 (100), 377 (10), 333 (17), 219 (31), 190 (90), 91 (45).
HRMS (EI): m/z calcd for C23H24N2O4 [M+]:
392.1736; found: 392.1719.
