Page 349 - Advanced Organic Chemistry Part B - Reactions & Synthesis

Ar ArSe 321
R′ R Se +
R′ SECTION 4.2
Nu R′ Nu R Electrophilic Cyclization
Nu R

Although exo cyclization is usually preferred, there is no strong prohibition of endo
cyclization and aryl-controlled regioselectivity can override the exo preference.

SePh
PhSeCl
PhCH=CH(CH ) CH OH
2
2 3
CH Cl 2 O
2
Ph Ref. 97
OH
OH O OH
H PhSeBr O SePh
CO 2 SePh +
Ph 2 equiv O O Ph
Ph
93:7
Ref. 98
Various electrophilic selenium reagents such as those described in Scheme 4.3
can be used. N-Phenylselenylphthalimide is an excellent reagent for this process
and permits the formation of large ring lactones. 99 The advantage of the reagent in
this particular application is the low nucleophilicity of phthalimide, which does not
compete with the remote internal nucleophile. The reaction of phenylselenenyl chloride
or N-phenylselenenylphthalimide with unsaturated alcohols leads to formation of -
phenylselenenyl ethers.
O
O
PhSe
CH CH OH + PhSeN
2
2
O Ref. 100
Another useful reagent for selenenylcyclization is phenylselenenyl triflate. This reagent
is capable of cyclizing unsaturated acids 101 and alcohols. 102 Phenylselenenyl sulfate
can be prepared in situ by oxidation of diphenyl diselenide with ammonium peroxy-
disulfate. 103

CH CHCH CH C(CH ) (PhSe) 2
2
3
3 2
CH 3 O C(CH ) 90%
3 2
+
OH (NH ) S O 8 2–
2 2
4
SePh
Several examples of sulfenylcyclization are given in Section A of Scheme 4.5.
Entry 1 is a 6-exo sulfenoetherification induced by phenylsulfenyl chloride. Entry 2
97 M. A. Brimble, G. S. Pavia, and R. J. Stevenson, Tetrahedron Lett., 43, 1735 (2002).
98
M. Gruttadauria, C. Aprile, and R. Noto, Tetrahedron Lett., 43, 1669 (2002).
99 K. C. Nicolaou, D. A. Claremon, W. E. Barnette, and S. P. Seitz, J. Am. Chem. Soc., 101, 3704 (1979).
100 K. C. Nicolaou, R. L. Magolda, W. J. Sipio, W. E. Barnette, Z. Lysenko, and M. M. Joullie, J. Am.
Chem. Soc., 102, 3784 (1980).
101
S. Murata and T. Suzuki, Chem. Lett., 849 (1987).
102 A. G. Kutateladze, J. L. Kice, T. G. Kutateladze, N. S. Zefirov, and N. V. Zyk, Tetrahedron Lett., 33,
1949 (1992).
103
M. Tiecco, L. Testaferri, M. Tingoli, D. Bartoli, and R. Balducci, J. Org. Chem., 55, 429 (1990).