Reformatsky reactions of a phenyl ketone, an alpha-bromoester, zinc dust, and a catalytic amount of iodine in dioxane under high-intensity ultrasound (HIU) irradiation from an ultrasonic probe give high yields of beta-hydroxyesters in short reaction times. A series of alkyl phenyl ketones with increasing steric demands of the alkyl group are evaluated as potential electrophiles for the reactions with several alpha-bromoesters, also having increasing steric demands. The Reformatsky reaction under HIU is found to be concentration dependent.

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Reactions of sym-(keto)dibenzo-16-crown-5 with ethyl α-bromoesters, zinc dust and iodine in dioxane and/or tetrahydrofuran under irradiation by high intensity ultrasound (HIU) provide β-hydroxy lariat ether esters in 79-91% yields. HIU-promoted Reformatsky reactions offer several advantages over customary thermal reaction conditions.

Reformatsky reactions of pentacyclo [5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane-8,11-dione (1) with ethyl bromoacetate and ethyl difluorobromoacetate have been performed in the presence zinc dust and iodine in dioxane under irradiation by high-intensity ultrasound (HIU). In each case, addition of one equivalent of the organozinc reagents occurs with concomitant intramolecular hemiacetal formation, thereby affording 3a (75% yield) and 3b (89% yield), respectively.

Synthesis of β-Lactams and β-Aminoesters via High Intensity Ultrasound-Promoted Reformatsky Reactions. -The title reaction affords good yields of either β-lactams (IV) or β-aminoesters (III) in short reaction times without the necessity to activate the zinc dust. Mixtures of both the products are only observed for 2 of the 16 aldimine educts examined. -(ROSS, N. A.; MACGREGOR, R. R.; BARTSCH*, R. A.; Tetrahedron 60 (2004) 9, 2035-2041; Dep. Chem. Biochem., Tex. Tech. Univ., Lubbock, TX 79409, USA; Eng.) -D. Singer 24-108