2260
H. E. Bartrum, R. F. W. Jackson
LETTER
(26) General Procedure for Iodotrimethylsilane Ring
(3) Liu, M.; Sibi, M. P. Tetrahedron 2002, 58, 7991.
(4) Cardillo, G.; Tomasini, C. Chem. Soc. Rev. 1996, 25, 117.
(5) Schreiber, J. V.; Frackenpohl, J.; Moser, F.; Fleischmann,
T.; Kohler, H. P. E.; Seebach, D. ChemBioChem 2002, 3,
424.
(6) Frackenpohl, J.; Arvidsson, P. I.; Schreiber, J. V.; Seebach,
D. ChemBioChem 2001, 2, 445.
(7) Cheng, R. P.; Gellman, S. H.; DeGrado, W. F. Chem. Rev.
2001, 101, 3219.
(8) Cole, D. C. Tetrahedron 1994, 50, 9517.
(9) Dexter, C. S.; Jackson, R. F. W.; Elliott, J. J. Org. Chem.
1999, 64, 7579.
Opening
Using conditions originally reported for the analogous
N-tosyl-protected lactone,15,16 iodotrimethylsilane (3 equiv)
was added dropwise to a solution of the lactone (1 equiv) and
EtOH (5 equiv) in dry CH2Cl2 under nitrogen at 0 °C. The
reaction was stirred for 3 h at 0 °C and 16 h at r.t. until TLC
analysis indicated complete consumption of starting
material, at which point aq Na2S2O3 solution (1 M) was
added. The organic layer was separated and washed with
brine, dried (MgSO4), and concentrated under reduced
pressure to afford the crude product, which was purified by
silica gel column chromatography.
(10) Dexter, C. S.; Hunter, C.; Jackson, R. F. W. J. Org. Chem.
2000, 65, 7417.
(27) Huo, S. Q. Org. Lett. 2003, 5, 423.
(11) Jackson, R. F. W.; Rilatt, I.; Murray, P. J. Chem. Commun.
2003, 1242.
(12) Rilatt, I.; Jackson, R. F. W. J. Org. Chem. 2008, 73, 8694.
(13) Bartrum, H. E.; Adams, H.; Caggiano, L.; Jackson, R. F. W.
Tetrahedron 2008, 64, 3701.
(14) Rilatt, I.; Caggiano, L.; Jackson, R. F. W. Synlett 2005,
2701.
(15) Jefford, C. W.; McNulty, J. Helv. Chim. Acta 1994, 77,
2142.
(16) Jefford, C. W.; Wang, J. B. Tetrahedron Lett. 1993, 34,
1111.
(17) Seki, M.; Shimizu, T.; Inubushi, K. Synthesis 2002, 361.
(18) Yoda, H.; Nakagami, Y.; Takabe, K. Tetrahedron:
Asymmetry 1994, 5, 169.
(19) Hanessian, S.; Schaum, R. Tetrahedron Lett. 1997, 38, 163.
(20) Lapidus, M.; Sweeney, M. J. Med. Chem. 1973, 16, 163.
(21) Gong, B.; Lynn, D. G. J. Org. Chem. 1990, 55, 4763.
(22) Procedure for Lactone Alkylation
(28) General Procedure for Pd-Catalysed Cross-Coupling
Zinc dust (195 mg, 3 mmol, 6 equiv) was placed in a dry 10
mL round-bottom flask with sidearm, containing a rugby-
ball-shaped magnetic stirrer. The flask was flushed with
nitrogen, and dry DMF (0.2 mL) was added under nitrogen
via syringe followed by catalytic iodine (40 mg, 0.15 mmol,
0.3 equiv). Effervescence was observed and the DMF
changed from colourless to yellow and back again. A
solution of the appropriate alkyl iodide (0.5 mmol) in DMF
(0.3 mL) under nitrogen was transferred to the activated zinc
suspension via syringe. The solution was stirred at r.t., and
the insertion proceeded with a noticeable exotherm. When
the solution had cooled, Pd2(dba)3 (11.0 mg, 0.0125 mmol,
2.5 mol%), P(o-tol)3 (15 mg, 0.05 mmol, 10 mol%) and the
aryl iodide (1.3 equiv relative to the alkyl iodide) were added
to the flask and the reaction stirred at r.t. overnight.
(29) Jackson, R. F. W.; Rilatt, I.; Murray, P. J. Org. Biomol.
Chem. 2004, 2, 110.
Using a minor modification of conditions already reported
for the alkylation of dianions of g-N-trifluoroacetyl amino
acid esters,19 n-BuLi (2.5 M in hexane, 5 mL, 12.5 mmol)
was added dropwise to a stirred solution of DIPA (1.9 mL,
13.75 mmol) in THF (5 mL) at 0 °C. The resulting solution
was stirred for 15 min before being cooled to –78 °C for the
addition of the lactone 6 (985 mg, 5 mmol) in THF (28 mL).
The reaction was stirred at the same temperature for a further
hour before the electrophile (5 equiv) was added dropwise
with careful monitoring of the internal temperature of the
reaction to ensure it did not exceed –78 °C. After stirring at
–78 °C for 18 h, the reaction was quenched with aq citric
acid (10%, 30 mL) before being extracted with EtOAc
(3 × 50 mL) and the organic fractions combined, washed
with brine (2 × 30 mL), dried (MgSO4) and evaporated
under reduced pressure. The crude product was purified by
silica gel column chromatography.
(30) Manolikakes, G.; Schade, M. A.; Hernandez, C. M.; Mayr,
H.; Knochel, P. Org. Lett. 2008, 10, 2765.
(31) Manolikakes, G.; Hernandez, C. M.; Schade, M. A.;
Metzger, A.; Knochel, P. J. Org. Chem. 2008, 73, 8422.
(32) General Procedure for Cu-Catalysed Allylation
The organozinc reagent was formed as described above
using zinc (6 equiv) and DMF (0.65 equiv) relative to the
alkyl iodide. While the zinc insertion was in progress,
CuBr·DMS (13 mol%) was dried gently under vacuum in a
separate flask until it changed from a white to a light green
powder. Dry DMF (0.65 equiv) was then added, followed by
the allyl chloride (1.3 equiv). Once the zinc insertion reached
completion, stirring of the reaction mixture was stopped to
allow the zinc powder to settle, and the supernatant was
transferred to the solution of allyl chloride and copper
catalyst via syringe. After stirring for 18 h at r.t., EtOAc (10
mL) was added and the reaction stirred for a further 15 min.
A further aliquot of EtOAc (30 mL) was added and the
organic layer separated and washed successively with aq
Na2S2O3 solution (1 M, 2 × 30 mL), H2O (30 mL) and brine
(30 mL), dried (MgSO4), and evaporated under reduced
pressure to afford the crude product which was purified by
silica gel column chromatography.
(23) Crystallographic data (excluding structure factors) for
compound 9 has been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
number CCDC 733395.
(24) Chung, S. J.; Chung, S.; Lee, H. S.; Kim, E. J.; Oh, K. S.;
Choi, H. S.; Kim, K. S.; Kin, Y. J.; Hahn, J. H.; Kim, D. H.
J. Org. Chem. 2001, 66, 6462.
(33) Meyer, C.; Marek, I.; Courtemanche, G.; Normant, J. F.
Tetrahedron Lett. 1993, 34, 6053.
(34) Meyer, C.; Marek, I.; Courtemanche, G.; Normant, J. F.
Tetrahedron 1994, 50, 11665.
(25) Park, J. I.; Tian, G. R.; Kim, D. H. J. Org. Chem. 2001, 66,
3696.
Synlett 2009, No. 14, 2257–2260 © Thieme Stuttgart · New York