Abstract
Alkynoic acids I-IV can be effectively cyclized to the corresponding exocyclic enol lactones with a new Rh(I) complex, [(cycphos)RhCl]2 (4) (cycphos = 1,2-bis(dicyclohexylphosphino)ethane), that we have developed. The high-yield lactonizations can be performed at room temperature, and methylene chloride appears to be the best solvent for the cyclization. Exclusive (Chemical Equation Presented) I R=H, n=1 II =CH3, n=1 II R=Ph, n=1 IV R=H, n=2 formation of Z-olefinic isomers was observed, i.e., trans addition of the carboxylate OH across the triple bond. There is also a strong preference for the formation of five- vs six-membered rings in the substituted pentynoic acid systems. Other electron-rich group VIII transition-metal complexes and mercuric salts were tested for catalytic activity under similar reaction conditions and were found to be less effective. The proposed mechanism involves initial OH activation by the metal center followed by nucleophilic attack of carboxylate anion on the metal-coordinated alkyne of the intermediate, and subsequent reductive elimination from the resulting hydrido-vinyl complex releases the lactone product and regenerates the catalyst.
| Original language | English |
|---|---|
| Pages (from-to) | 6385-6388 |
| Number of pages | 4 |
| Journal | Journal of the American Chemical Society |
| Volume | 109 |
| Issue number | 21 |
| Publication status | Published - 1987 |
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ASJC Scopus subject areas
- Chemistry(all)
Cite this
Transition-metal-catalyzed cyclization of alkynoic acids to alkylidene lactones. / Chan, Dominic M T; Marder, Todd B.; Milstein, David; Taylor, Nicholas J.
In: Journal of the American Chemical Society, Vol. 109, No. 21, 1987, p. 6385-6388.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Transition-metal-catalyzed cyclization of alkynoic acids to alkylidene lactones
AU - Chan, Dominic M T
AU - Marder, Todd B.
AU - Milstein, David
AU - Taylor, Nicholas J.
PY - 1987
Y1 - 1987
N2 - Alkynoic acids I-IV can be effectively cyclized to the corresponding exocyclic enol lactones with a new Rh(I) complex, [(cycphos)RhCl]2 (4) (cycphos = 1,2-bis(dicyclohexylphosphino)ethane), that we have developed. The high-yield lactonizations can be performed at room temperature, and methylene chloride appears to be the best solvent for the cyclization. Exclusive (Chemical Equation Presented) I R=H, n=1 II =CH3, n=1 II R=Ph, n=1 IV R=H, n=2 formation of Z-olefinic isomers was observed, i.e., trans addition of the carboxylate OH across the triple bond. There is also a strong preference for the formation of five- vs six-membered rings in the substituted pentynoic acid systems. Other electron-rich group VIII transition-metal complexes and mercuric salts were tested for catalytic activity under similar reaction conditions and were found to be less effective. The proposed mechanism involves initial OH activation by the metal center followed by nucleophilic attack of carboxylate anion on the metal-coordinated alkyne of the intermediate, and subsequent reductive elimination from the resulting hydrido-vinyl complex releases the lactone product and regenerates the catalyst.
AB - Alkynoic acids I-IV can be effectively cyclized to the corresponding exocyclic enol lactones with a new Rh(I) complex, [(cycphos)RhCl]2 (4) (cycphos = 1,2-bis(dicyclohexylphosphino)ethane), that we have developed. The high-yield lactonizations can be performed at room temperature, and methylene chloride appears to be the best solvent for the cyclization. Exclusive (Chemical Equation Presented) I R=H, n=1 II =CH3, n=1 II R=Ph, n=1 IV R=H, n=2 formation of Z-olefinic isomers was observed, i.e., trans addition of the carboxylate OH across the triple bond. There is also a strong preference for the formation of five- vs six-membered rings in the substituted pentynoic acid systems. Other electron-rich group VIII transition-metal complexes and mercuric salts were tested for catalytic activity under similar reaction conditions and were found to be less effective. The proposed mechanism involves initial OH activation by the metal center followed by nucleophilic attack of carboxylate anion on the metal-coordinated alkyne of the intermediate, and subsequent reductive elimination from the resulting hydrido-vinyl complex releases the lactone product and regenerates the catalyst.
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M3 - Article
VL - 109
SP - 6385
EP - 6388
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 21
ER -