1. Ultrasound assisted lipase catalyzed synthesis of poly-6-hydroxyhexanoate
A M Gumel, M S M Annuar, Y Chisti, T Heidelberg Ultrason Sonochem. 2012 May;19(3):659-67. doi: 10.1016/j.ultsonch.2011.10.016. Epub 2011 Nov 7.
Ultrasonic irradiation greatly improved the Candida antarctica lipase B mediated ring opening polymerization of ε-caprolactone to poly-6-hydroxyhexanoate in the ionic liquid 1-ethyl-3-methylimidazolium tetraflouroborate. Compared to the conventional nonsonicated reaction, sonication improved the monomer conversion by 63% and afforded a polymer product of a narrower molecular weight distribution and a higher degree of crystallinity. Under sonication, the polydispersity index of the product was ~1.44 compared to a value of ~2.55 for the product of the conventional reaction. With sonication, nearly 75% of the monomer was converted to product, but the conversion was only ~16% for the reaction carried out conventionally. Compared to conventional operation, sonication enhanced the rate of polymer propagation by >2-fold and the turnover number of the lipase by >3-fold.
2. Ultrasound promoted synthesis of some novel fused pyrans
Tamer S Saleh, Naglaa M Abd El-Rahman, Ahmed A Elkateb, Nehal O Shaker, Naema A Mahmoud, Shimaa A Gabal Ultrason Sonochem. 2012 May;19(3):491-7. doi: 10.1016/j.ultsonch.2011.10.008. Epub 2011 Nov 3.
Novel fused pyrans were synthesized from the reaction of the tetrahydropyran-4-one with arylidine malononitriles. Different fused pyran derivatives were obtained from the mentioned reaction depending on type of catalyst used and type of energy used. Reactions were carried out under silent and ultrasonic conditions. In general, it was found that sometimes ultrasound irradiations change the reaction path in comparing with silent condition. In addition to improvement in reaction times, the products were obtained in high yields and their structures were determined by elemental analyses, spectral data.
3. Efficient one-pot three-component synthesis of N-(4-arylthiazol-2-yl) hydrazones in water under ultrasound irradiation
Dong-Nuan Zhang, Ji-Tai Li, Ya-Li Song, Hui-Min Liu, Hong-Ya Li Ultrason Sonochem. 2012 May;19(3):475-8. doi: 10.1016/j.ultsonch.2011.10.017. Epub 2011 Nov 10.
A highly efficient and facile one-pot three-component synthesis of N-(4-arylthiazol-2-yl) hydrazones was carried out in excellent yield without any catalyst in water under ultrasound irradiation.