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Large amounts of waste may result from the neutralization of homogeneous acid catalysts following reaction. Here we present examples of in situ acid formation and self-neutralization, thus eliminating waste and offering advantages for product recovery. The formation of a-terpineol (2) from b-pinene (1) is a reaction of commercial significance that is typically run with strong acid. We demonstrate that the reaction can be performed under more environmentally benign conditions using the in situ acid formation capabilities of two different green technologies: CO 2 expanded liquids and reactions in hot water (200 °C). This work presents an example of the application of these methods to a reaction that has commercial significance and adds to our knowledge about the benefits and effects of co-solvents. The relative rates and product distributions achieved in each system are presented and discussed.

45 °C for 0.5 h. Sodium hydride (0.25 mmol) (10 mg of 60% NaH dispersed in mineral oil washed with petroleum ether) was added to the solution. After cessation of gas evolution 0.5 mL of 5% DC1 was added. TLC on silica gel (9% MeOH in CH2C12, UV visualization) showed only the ring-contracted product 3 had formed; this was confirmed by proton NMR on the reaction mixture.Acknowledgment. We thank E. Reich for elemental analyses, M. Mentzer for mass spectral data, and D. Staiger and G. Zuber for some of the NMR data. We acknowlede the encouragement of Dr. G. Dunn.

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