Anti-Markovnikov addition of thiols across double bonds catalyzed by H- Rho-zeolite

Article abstract of DOI:10.1055/s-1999-2976

A variety of olefins react with thiols in the presence of a catalytic amount of H-Rho-zeolite to afford the corresponding anti-Markovnikov addition products in good to excellent yields.

Full text of DOI:10.1055/s-1999-2976

LETTER
1921
Anti-Markovnikov Addition of Thiols Across Double Bonds Catalyzed by
H-Rho-Zeolite
Pradeep Kumar,* Rajesh Kumar Pandey, Vishnumurthy R. Hegde
Division of Organic Chemistry : Technology, National Chemical Laboratory, Pune-411008, INDIA
Fax 0091-20-5893614; E-mail: tripathi@dalton.ncl.res.in
Received 29 September 1999
sponding anti-Markovnikov products were obtained in
good to excellent yields (Table). In a typical reaction pro-
cedure, to a stirred solution of olefin 1 (20 mmol) in n-
hexane (25 ml) were added H-Rho-zeolite (0.5 equivalent
by wt. of olefin) and thiol 2 (25 mmol) and the mixture
was refluxed with stirring for the indicated length of time
(Table). The reaction was monitored by TLC and G. C.
After the completion of reaction, zeolite was filtered off
and washed with n-hexane; the filtrate was then washed
with 10% aq. NaOH solution to remove excess thiol and
then further washed with water, brine and dried over
Na2SO4. Removal of solvent and subsequent silica gel
column chromatography afforded the pure product 3
which was analyzed by 1H NMR. Much to our surprise, an
anti-Markovnikov addition product was obtained which
otherwise formed in the presence of peroxide. Due to ster-
ic constraints on the diffusional path of the molecules im-
posed by the different structural feature of the zeolite, the
more bulkier Markovnikov adduct could not be retained in
the zeolite pore and presumably for this reason only the
anti-Markovnikov product was obtained. The mechanism
of anti-Markovnikov addition could be compared with
those mediated by the free-radical initiators where the
main effect also seems to be steric and thus the only com-
pound obtained is the sterically preferred anti-Markovni-
kov product.5 The present procedure for thiol addition to
an olefin is quite general as a wide range of olefins such
as terminal, internal, cyclic, acyclic and branched olefins
can be reacted with thiols easily under mild conditions.
Under the reactions conditions employed, styrene reacted
smoothly with a variety of thiols to afford the anti-Mark-
ovnikov products (Table, entries 1 & 4) and no polymer-
ization of styrene could be observed. Similarly α-
methylstyrene on reaction with thiophenol afforded the
corresponding addition product in excellent yield (Table,
entry 2). Mention must be made here that the reaction of
thiophenol with olefin did not yield any Friedel-Crafts ad-
dition product and ethanethiol also reacted smoothly un-
der the reaction conditions.7
Abstract: A variety of olefins react with thiols in the presence of a
catalytic amount of H-Rho-zeolite to afford the corresponding anti-
Markovnikov addition products in good to excellent yields.
Key words: anti-Markovnikov addition, H-Rho-zeolite, thiols, ole-
fins, heterogeneous catalysis
The last few years have witnessed a considerable upsurge
of interest in the area of zeolite induced organic trans-
formations.1 In a series of publications from our group,2
we have exploited the catalytic potential of zeolites for
various organic synthetic transformations, e.g. thioacetal-
ization of carbonyl compounds, sulfoxidation of thio-
ethers, deketalization, tetrahydropyranylation of alcohols,
oxidative cleavage of tosylhydrazones, methoxymethyl-
ation of alcohols, chemo- and stereoselective epoxidation
and acetylation of aldehydes etc. In continuation, we wish
to report a mild, convenient and heterogeneous catalytic
methodology for the synthesis of anti-Markovnikov addi-
tion products by the reaction of thiols and olefins using
Rho-zeolite.
In general, the protic acid3 or Lewis acid4 catalyzed addi-
tion of thiols across double bonds is known to give thio-
ethers having structures which are in accordance with
Markovnikov’s rule. However, in the presence of free-
radical initiator, thiols have been reported to add to double
or triple bonds in anti-Markovnikov fashion by a free-
radical mechanism.5 A variety of hydroboration reagents
developed for this reaction are also reported to give the
anti-Markovnikov product.6 However, the use of conven-
tional protic or Lewis acid catalysts entails the problem of
corrosivity, work-up and effluent pollution. Consequent-
ly, there is genuine need for an efficient and heteroge-
neous catalytic method for this reaction using inexpensive
and nonpolluting reagents. Now we report that H-Rho-
zeolite serves as an efficient catalyst for the thiol addition
to olefins (Scheme).
In conclusion, we have established a facile, heterogeneous
catalytic method for the anti-Markovnikov addition of thi-
ols to a variety of olefinic compounds. The obvious ad-
vantages of heterogeneous catalysis in terms of easy
separation, consistent yields and recyclability of the cata-
lyst are noteworthy. Thus, the present catalytic method
should serve as a useful addition to synthetic organic
chemistry.
Scheme
Thus, when the olefins were treated with thiols in the pres-
ence of catalytic amount of H-Rho-zeolite, the corre-
Synlett 1999, No. 12, 1921–1922 ISSN 0936-5214 © Thieme Stuttgart · New York

1922
P. Kumar et al.
LETTER
Acknowledgement
(4) (a) Mukaiyama, T.; Izawa, T.; Saigo, K; Takai, H. Chem.
Lett.1973, 335. (b) Belley, M. Zamboni, R. J.Org.
Chem.1989, 54, 1230.
(5) For review of free-radical addition of mercaptans, see :
Griesbaum, K. Angew. Chem. Int. Ed. Engl. 1970, 9, 273.
(6) For a review of haloboranes, see; Brown, H. C.; Kulkarni, S.
U. J. Organomet. Chem. 1982, 239, 23.
VRH thanks CSIR, New Delhi for a research fellowship. RKP
thanks Director, NCL for allowing him to work as a guest worker.
We are grateful to Dr. T. Ravindranathan, Head, Organic Chemi-
stry: Technology Division for his constant encouragement and sup-
port.
(7) The reaction of the thiophenol and olefin is reported to give
the Friedel-Crafts product while alkylthiols failed to give any
addition product see : ref. 3c.
(8) H-Rho-zeolite was procured as a gift sample from Catalysis
Division, NCL, Pune. Prior to use it was calcined at 500 0C in
the presence of air.
References and Notes
This is NCL Communication No. 6474.
(1) (a) Davis, M. E. Acc. Chem. Res. 1993, 26, 111. (b) Holderich,
W.; Hesse, M.; Naumann, F. Angew. Chem. Int. Ed. Engl.
1988, 27,226. (c) Suib, S. L. Chem. Rev. 1993, 93, 803.
(d) Sachtler, W. M. H. Acc. Chem. Res.1993, 26, 383.
(e) Kumar, P.; Kumar, R.; Pandey, B. J. Ind. Inst. Sci. 1994,
74, 293.
(9) Selected spectroscopic data: 3a : colorless liquid; IR νmax
/
cm-1 (Neat) : 693, 748, 1080, 1439, 1475, 1578, 2850, 2920;
1H NMR(CDCl3, 200 MHz) δ : 2.9 (t, J = 6.8 Hz, 2H), 3.25 (t,
J = 6.8 Hz, 2H), 7.2 – 7.55 (m,10H); MS (m/z, rel.int%) :
M+214 (60), 185 (5),154 (6), 123 (6), 110 (100), 109 (40), 91
(2) For an account of an oxidative transformations catalyzed by
titanium and vanadium silicate molecular sieves, see :
(a) Kumar, P.; Kumar, R.; Pandey, B. Synlett 1995, 289.
(b) Kumar, P.; Reddy, R. S.; Singh, A. P.; Pandey, B.
Tetrahedron Lett. 1992, 33, 825. Synthesis 1993, 67.
(c) Reddy, R. S.; Reddy, J. S.; Kumar, R.; Kumar, P. J. Chem.
Soc., Chem. Commun.1992, 84. (d) Rao, M. N.; Kumar, P.;
Singh, A. P.; Reddy, R. S. Synth. Commun. 1992, 1299.
(e) Kumar, P; Dinesh, C. U.; Reddy, R. S.; Pandey, B.
Synthesis 1993, 1069. (f) Kumar, P.; Hegde, V. R.; Pandey,
B.; Ravindranathan, T. J. Chem. Soc., Chem. Commun.1993,
1553. (g) Kumar, P.; Raju, S. V. N.; Reddy, R. S.; Pandey, B.
Tetrahedron Lett. 1994, 35,1289. (h) Kumar, R.; Pais, G. C.
G.; Pandey, B.; Kumar, P. J. Chem. Soc., Chem. Commun.
1995, 1315. (i) Kumar, P.; Hegde, V. R.; Kumar, T. P.
Tetrahedron Lett.1995, 36,601.
(18), 77 (35), 69 (10), 65 (30). 3b : colorless liquid; IR νmax
/
cm-1(Neat) : 690, 749, 1080, 1439, 1478, 1579, 2849, 2920; 1H
NMR(CDCl3, 200 MHz) δ : 1.25 (d, J = 6.8 Hz, 3H), 3.0 (m,
1H), 3.45 (m, 2H), 7.2 – 7.5 (m, 10H); MS (m/z, rel.int%) :
M+228 (8), 213 (12), 185 (5), 154 (5), 137 (10), 123 (95), 110
(100), 91 (50), 77 (60), 65 (45). 3h : colorless liquid; IR νmax
/cm-1(Neat) : 686, 732, 1021, 1083, 1371, 1464, 1577, 2851,
2919; 1H NMR(CDCl3, 200 MHz) δ :0.9 (t, J = 6.8 Hz, 3H),
1.2 – 1.5 (m, 8H), 1.67 (m, 4H), 2.93 (t, J = 6.8 Hz, 2H), 7.2
– 7.4 (m, 5H); MS (m/z, rel.int%) : M+222 (55), 165 (2), 135
(5), 123 (56), 110 (100), 91 (9), 77 (20), 65 (13), 57 (2). 3k :
colorless liquid; IR νmax/ cm-1(Neat) : 667, 691, 747, 903,
1023, 1088, 1429, 1477, 1581, 2249, 2930; 1H NMR(CDCl3,
200 MHz) δ : 2.65 (t, J = 6.8 Hz, 2H), 3.15 (t, J = 6.8 Hz, 2H),
7.2 – 7.7 (m, 5H); MS: (m/z, rel.int%) M+163 (64), 135 (3),
123 (100), 109 (36), 91 (8), 77 (42), 69 (30), 65 (49), 59 (3).
(3) (a) Posner, T. Ber.1905, 38, 649. (b) Secrettas, C. G.; Mieha-
Secrettas, M. J. Org. Chem.,1979, 44, 713. (c) Wolf, F.; Finke,
H. Z. Chem. 1972, 12, 180.
Article Identifier:
1437-2096,E;1999,0,12,1921,1922,ftx,en;L12599ST.pdf
Synlett 1999, No. 12, 1921–1922 ISSN 0936-5214 © Thieme Stuttgart · New York