Efficient Synthesis of a New Type of Baylis–Hillman Adducts and Their Stereoselective Bromination

Abstract

A new type of Baylis–Hillman adducts derived from chlorovinyl aldehydes were prepared via Vilsmeier reaction of ketones with a bis(trichloromethyl) carbonate (BTC)/DMF system to construct chlorovinyl aldehydes, followed by sonochemical Baylis–Hillman reaction under solvent-free conditions. The stereoselective bromination of these new compounds with a Br₂-Ph₃P system has been achieved efficiently with good to excellent yields under mild conditions.

Keywords:

• Baylis–Hillman reaction
• bromination
• stereoselective
• ultrasonic
• Vilsmeier reaction

ACKNOWLEDGMENTS

We thank the National Key Technology Research and Development Program (No. 2007BAI34B00) and the National Natural Science Foundation of China (No. 20676123) for financial support.

Notes

^a Reaction conditions: 1 (100.0 mmol), BTC (100.0 mmol), DMF (300.0 mmol), and chloroform (100 mL) were used.

^b Isolated yields based on 1.

^a Reaction conditions: 2a (50.0 mmol), 3a (100.0 mmol), base (10.0 mmol), and solvent (50 mL) were used.

^b Isolated yields based on 2a.

^c In the absence of ultrasound.

^a Reaction conditions: 2 (50.0 mmol), 3 (100.0 mmol), and DABCO (10.0 mmol) were used.

^b Isolated yields based on 2.

^c In the absence of ultrasound.

^a Reaction conditions: 4a (10.0 mmol), bromination reagents (10.0 mmol), and solvents (30 mL) were used.

^b Isolated yields.

^a Reaction conditions: 4 (10.0 mmol), Br₂ (10.0 mmol), Ph₃P (10.0 mmol), and CH₂Cl₂ (30 mL) were used.

^b Isolated yields.