Palladium-catalyzed highly diastereoselective cyclic carbopalladation-carbonylative esterification tandem reaction of iododienes and iodoarylalkenes

Article abstract of DOI:10.1021/ol9900663

(Equation Presented) Pd-catalyzed reaction of iododienes and iodoarylalkenes represented by 1, 8, and 10 under 1 atm of CO and a small amount of O₂ in the presence of a base, e.g., NEt₃, as well as MeOH and H₂O in DMF can

Full text of DOI:10.1021/ol9900663

ORGANIC
LETTERS
1999
Vol. 1, No. 1
165-167
Palladium-Catalyzed Highly
Diastereoselective Cyclic
Carbopalladation−Carbonylative
Esterification Tandem Reaction of
Iododienes and Iodoarylalkenes†
Christophe Cope´ret and Ei-ichi Negishi*
Department of Chemistry, Purdue UniVersity, West Lafayette, Indiana 47907
negishi@purdue.edu
Received May 3, 1999
ABSTRACT
Pd-catalyzed reaction of iododienes and iodoarylalkenes represented by 1, 8, and 10 under 1 atm of CO and a small amount of O in the
2
presence of a base, e.g., NEt3, as well as MeOH and H O in DMF can undergo a highly diastereoselective cyclic carbopalladation−carbonylative
2
esterification tandem process (Type II C−Pd process) to give in high yields the corresponding ester-containing cyclization products, e.g., 2,
9, and 11, in as high as 98% diastereoselectivity.
Herein reported is a diastereoselective cyclic carbopallada-
tion-esterification tandem process1 displaying 1,4-chirality
transfer in as high as 98% diastereoselectivity, as demon-
strated by the transformations (1 f 2) shown in Scheme 1.
Coupled with various known asymmetric syntheses of allylic
alcohols,2 this reaction promises to provide a stereocontrolled
route to various cyclic natural products, as exemplified by
the conversion of 2a into the Colvin-Raphael lactone3 (5),
which has served as an intermediate for trichodermin3 (6)
and trichodiene4 (7) (Scheme 2).
The cyclic carbopalladation-carbonylative esterification
was discovered by us5 as an unwanted side reaction of cyclic
acylpalladation of alkynes. This process, termed Type II
C-Pd process1a hereafter to distinguish it from the more
conventional cyclic carbopalladation terminated by the Heck
alkene substitution (Type I C-Pd process), has since been
shown to be a useful method for terminating cascade cyclic
carbopalladation.6 The Type II C-Pd process has also been
applied to the cyclization of iododienes and iodooligoenes.7
With iodoalkenes, at least one asymmetric carbon center is
generated. Although chirality transfer in the Type I C-Pd
† This paper is dedicated to Professor R. Keese of the University of Bern
on the occasion of his 65th birthday.
(4) (a) Welch, S. C.; Rao, A. S. C. P.; Wong, R. Y. Synth. Commun.
1976, 6, 443. (b) Welch, S. C.; Gibbs, W. R. Synth. Commun. 1976, 6,
485.
(5) Zhang, Y.; Negishi, E. J. Am. Chem. Soc. 1989, 111, 3454.
(6) (a) Sugihara, T.; Cope´ret, C.; Owczarczyk, Z.; Harring, L. S.; Negishi,
E. J. Am. Chem. Soc. 1994, 116, 7923. (b) Cope´ret, C.; Sugihara, T.; Negishi,
E. Tetrahedron Lett. 1995, 36, 1771. (c) Cope´ret, C.; Ma, S.; Sugihara, T.;
Negishi, E. Tetrahedron 1996, 52, 11529.
(7) (a) Grigg, R.; Kennewell, P.; Teasdale, A. J. Tetrahedron Lett. 1992,
33, 7789. (b) Grigg, R.; Sridharan, V. Tetrahedron Lett. 1993, 34, 7471.
(c) Brown, A.; Grigg, R.; Ravishankar, T.; Thornton-Pett, M. Tetrahedron
Lett. 1994, 35, 2753. (d) Grigg, R.; Redpath, J.; Sridharan, V.; Wilson, D.
Tetrahedron Lett. 1994, 35, 4429. (e) Negishi, E.; Ma, S.; Amanfu, J.;
Cope´ret, C.; Miller, J. A.; Tour, J. M. J. Am. Chem. Soc. 1996, 118, 5919.
(1) (a) For background information on cyclic carbopalladation, see:
Negishi, E.; Cope´ret, C.; Ma, S.; Liou, S. Y.; Liu, F. Chem. ReV. 1996, 96,
365 and references therein. (b) For some examples of diastereoselective
cyclic carbopalladation reactions of 1,1-disubstituted alkenes without the
involvement of CO, see: Overman, L. E. Pure Appl. Chem. 1994, 66, 1423.
(2) See, for example: (a) Midland, M. M.; McDowell, D. C.; Hatch, R.
L.; Tramontano, A. J. Am. Chem. Soc. 1980, 102, 867. (b) Brown, H. C.;
Ramachandran, P. V. Pure Appl. Chem. 1991, 63, 307. (c) Brown, H. C.;
Ramachandran, P. V. Acc. Chem. Res. 1992, 25, 16. (d) Matsumura, K.;
Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1997, 119, 8738.
(3) (a) Colvin, E. W.; Raphael, R. A.; Roberts, J. S. Chem. Commun.
1971, 858. (b) Colvin, E. W.; Malchenko, S.; Raphael, R. A.; Roberts, J.
S. J. Chem. Soc., Perkin Trans. 1 1973, 1989.
10.1021/ol9900663 CCC: $18.00 © 1999 American Chemical Society
Published on Web 05/25/1999

Scheme 1
transfer has also been observed in the formation of a five-
Scheme 2
membered ring (10 f 11). On the other hand, the corre-
sponding reaction of 8b protected with a CH3OCH2 (MOM)
group gives a 1:1 diastereomeric mixture in 94% NMR yield.
These results can be rationalized on the basis of the following
assumptions. (i) The reaction must proceed via a boat or
boatlike transition state.1b (ii) For carbopalladation, which
may be thought to proceed by a concerted process, the C-Pd
bond and the interacting C-C π-bond must become es-
sentially coplanar. Even simple molecular models readily
indicate that the proposed boatlike conformation would be
by far the most favorable one for satisfying the second
assumption. (iii) Whereas the bulky TBSO group strongly
favors the pseudoequatorial orientation, this tendency is
counterbalanced by the chelation effect favoring the axial
orientation of the MOM group in the latter case (Scheme
3). Although the stereochemistry assigned to 2, 9, and 11
was consistent with both their NMR spectral data and the
interpretation presented above, an unequivocal establishment
of the stereochemistry depended on the X-ray crystal-
lographic analysis of the p-nitrobenzoyl derivative of 2b (R
) n-Bu).
It is noteworthy that the diastereoselectivity also signifi-
cantly depends on the method of termination of carbo-
palladation. Thus, the Pd-catalyzed bicyclization reaction of
1c in the absence of CO and MeOH gave a 2:1 mixture of
cis- and trans-12 along with a minor amount (<3-5%) of
13 (Scheme 4). The observed low diastereoselectivity may
also be due, in part, to the presence of a homoallyl group
that can exert a chelation effect. Clearly, further studies are
necessary to clarify these intricate stereochemical details.
Nonetheless, it does appear that the carbonylative trapping
of organopalladium intermediates (Type II C-Pd process)
offers favorable features which may not be shared by the
more usual Type I C-Pd process. It should also be pointed
out that, in sharp contrast with the previously developed
cyclic acylpalladation reactions,7e,10 the Type II C-Pd
reaction requires alkynes and 1,1-disubstituted alkenes. Thus,
for example, the reaction of 14 under the conditions that are
satisfactory for the Type II C-Pd reaction of 1, 8, and 10,
process mainly in conjunction with the formation of spiro-
cycles has been investigated,1b,8 little or nothing has been
investigated regarding chirality transfer in the Type II C-Pd
process.
The following findings pertinent to observing high-yielding
and highly diastereoselective Type II C-Pd processes are
noteworthy. (1) As reported earlier,7e favorable Type II C-Pd
processes have been observed in a medium consisting of
1:2:0.1 MeOH-DMF-H2O, and it is essential to heat the
reaction mixture at reflux to minimize premature esterifica-
tion, i.e., the formation of 4 in Scheme 1. (2) Although
Pd-induced cyclopropanation5,9 can be a significant side
reaction,7e none of the substrates shown in Scheme 1 gave
cyclopropanation products in detectable yields under the
indicated conditions. (3) Selection of the hydroxy protecting
group is also critically important. Thus, for example, the
reaction of 8a protected with a bulky t-BuMe2Si (TBS
hereafter) group leads to the formation of 9a in 94% NMR
yield in 98% diastereoselectivity. The same sense of chirality
(8) (a) Abelman, M. M.; Overman, L. E. J. Am. Chem. Soc. 1988, 110,
2328. (b) Abelman, M. M.; Overman, L. E.; Tran, V. D. J. Am. Chem. Soc.
1990, 112, 6959. (c) Overman, L. E.; Ricca, D. J.; Tran, V. D. J. Am. Chem.
Soc. 1993, 115, 2042.
(9) Owczarczyk, Z.; Lamaty, F.; Vawter, E. J.; Negishi, E. J. Am. Chem.
Soc. 1992, 114. 10091.
166
Org. Lett., Vol. 1, No. 1, 1999

Scheme 3
Scheme 5
group. This effect is absent in 18 formed via cyclic
carbopalladation (Scheme 5).
With 2a (R ) H) in hand, we converted it into the Colvin-
Raphael lactone 53,4 in 44% overall yield by (i) treatment
with Bu4NF followed by oxidation with (COCl)2 and DMSO
and (ii) addition of MeMgCl to the ketone followed by
lactonization and elimination according to the literature
procedure3,4 (Scheme 2).
Scheme 4
The required iodoallyl alcohols 1 are readily preparable
via reduction of the corresponding propargylic alcohols with
LiAlH4 and NaOMe11 followed by iodinolysis. Since
propargyl alcohols are enantioselectively preparable by
known methods,2 the overall process can, in principle, be
enantioselective.
Acknowledgment. We thank the National Institutes of
Health (GM 36792) for support of this research, Johnson-
Matthey for palladium compounds, and Purdue University
for providing a Graduate Fellowship to C.C. We also thank
Dr. P. Fanwick of our department for X-ray analytical
service.
i.e., condition A in Scheme 3, little or none of the desired
product 15 was obtained, the only products obtained in 54%
combined yield being a roughly 2:1 mixture of the cyclic
Heck reaction products (Type I C-Pd) 16a and 16b1
(Scheme 5). It appears reasonable to propose that, in the
previously developed cyclic acylpalladation-carbonylative
esterification tandem process (Type II Ac-Pd), cyclized
organopalladium intermediates 17 are stabilized against
dehydropalladation through chelation with the carbonyl
Supporting Information Available: Experimental pro-
cedures and spectroscopic data for compounds 1a-d, 8a,b,
and 10 and crystallographic data for the p-nitrobenzoyl
derivative of 18e. This material is available free of charge
via the Internet at http://pubs.acs.org.
OL9900663
(10) (a) Tour, J. M.; Negishi, E. J. Am. Chem. Soc. 1985, 107, 8289. (b)
Negishi, E.; Wu, G.; Tour, J. M. Tetrahedron Lett. 1988, 29, 6745. (c)
Negishi, E.; Cope´ret, C.; Ma, S.; Mita, T.; Sugihara, T.; Tour, J. M. J. Am.
Chem. Soc. 1996, 118, 5904.
(11) Corey, E. J.; Katzenellenbogen, J. A.; Posner, G. H. J. Am. Chem.
Soc. 1967, 89, 4245.
Org. Lett., Vol. 1, No. 1, 1999
167