Crabbé allene synthesis

What is Crabbé allene synthesis?

The Crabbé allene synthesis yields either non-alkylated allenes or alkylated allenes in good amounts when using organocuprate reagents and prop-2-ynylic acetates as starting materials.

Crabbé allene synthesis
Crabbé allene synthesis

Experimental procedure

PhSCu (4.41 g; 25.5 mmol) was suspended in Et2O (100 mL) at -35 ºC, and 2.47M BuLi in hexane (9.91 mL; 2.45 mmol) was added to the mixture. After 20 minutes at -30°C, reactive 1 (2.26 g; 10.2 mmol) in Et2O (35 mL) was slowly added dropwise at -78°C. The mixture was stirred for 1 hour and then quenched with 2 mL of saturated NH4Cl at a rate of 0.16 mL/min. The solids were left to stir for 6 hours at -78°C before warming to 20 ºC and filtering. The organic phase was washed, evaporated, and purified using chromatography, and 1.51 g of product 2 is obtained with a 91 % yield.

References

Pierre Crabbé, Eliezer Barreiro, Jean-Marie Dollat and Jean-Louis Luche
Controlled formation of allenes with organocuprates J. Chem. Soc., Chem. Commun., 1976, 183-184
DOI: 10.1039/C39760000183

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