Kinetics of the Uncatalyzed Hydrostannation of Diethyl Acetylenedicarboxylate

Abstract

Hydrostannation of carbon–carbon triple bonds is usually catalyzed by a free radical initiator or by metal complexes of palladium, molybdenum or rhodium. However, when the triple bond is substituted with an effective electron‐withdrawing group, the addition reaction will proceed in the absence of a catalyst. In this paper we report the kinetics of hydrostannation of diethyl acetylenedicarboxylate, (1), with trimethylstannane (2a), tri‐n‐propylstannane (2b), tri‐n‐butylstannane (2c), and triphenylstannane, (2d). Rate constants for these reactants were determined in acetonitrile at 25, 35, and 45 °C. Also, rate constants for trimethylstannane and tripropylstannane were determined in cyclohexane and trimethylstannane‐d₁ (2e), in acetonitrile. Finally, the hydrostannation with tributylstannane was run at 25, 35, and 45 °C in 95% ethanol. Where appropriate, enthalpies and entropies of activation were determined.

Keywords:

• Uncatalyzed hydrostannation
• Kinetics
• Activation parameters
• Solvent effects
• Deuterium isotope effects

Acknowledgments

This work was supported, in part, by the NSF‐REU Program and the Colgate University Research Council. This support is gratefully acknowledged. We thank Ben Leslie for technical assistance.

Notes

^aA search of Chemical Abstracts Plus using Scifinder Scholar from 1998–2002 yielded 35 references to the use of vinylstannanes in Stille coupling reactions and 18 other references to the use of vinylstannanes in organic syntheses.