Page 788 - Advanced Organic Chemistry Part B - Reactions & Synthesis

764 Triple bonds can also participate in the metathesis reaction. Intramolecular
reactions give vinylcycloalkenes, whereas intermolecular reactions provide conjugated
CHAPTER 8 dienes. 301 The mechanism is similar to that for -diene metathesis, but in contrast
Reactions Involving to diene cyclization, no carbon atoms are lost. 302
Transition Metals

M M M M M
X X X X +
X

Intramolecular alkene-alkyne metathesis
M M M M +
M +
R R
R
R R
Intermolecular alkene-alkyne metathesis

The reaction has been applied in several synthetic contexts. The intermolecular reaction
has been used to construct the conjugated diene side chain of mycothiazole, an
antibiotic isolated from a sponge.

cat F OTs
TBDPSO + TBDMSO
OTs
1.1:1 E:Z mixture
Ref. 303

The intermolecular version has been used in alkaloid synthesis.

CH 3
CH 3 F
N O N O
H
73% Ref. 304

When the intramolecular version is applied to silyloxyalkynes, the ultimate products
are acetyl cycloalkenes. 305

C COTIPS OTIPS O
X H CH 3
X X
CH CH CH 2
2
X = (CH 2 ) n , (CH 2 ) n O, (CH 2 ) n NCO 2 CH 3
or fused ring
This reaction was used to prepare an intermediate suitable for synthesis of the sesquiter-
penes - and -eremophilane and related structures. 306
301
S. T. Diver and A. J. Giessert, Synthesis, 466 (2004).
302 R. Stragies, M. Schuster, and S. Blechert, Angew. Chem. Int. Ed. Engl., 36, 2518 (1997).
303
S. Rodriguez-Conesa, P. Candal, C. Jimenez, and J. Rodriguez, Tetrahedron Lett., 42, 6699 (2001).
304 A. Kinoshita and M. Mori, J. Org. Chem., 61, 8356 (1996).
305 M. P. Schramm, D. S. Reddy, and S. A. Kozmin, Angew. Chem. Int. Ed. Engl., 40, 4274 (2001).
306
D. S. Reddy and S. A. Kozmin, J. Org. Chem., 69, 4860 (2004).