The sodium tungstate catalyzed oxidation of 1,2,3,4-tetrahydroquinolines (1) with 30% aqueous hydrogen peroxide solution in methanol gives l-hydroxy-3,4-dihydroquinolin-2(lH)-ones (2), which are important biologically active compounds, in good to excellent yields. The cyclic hydroxamic acid 7 is also obtained in good yield. Since reduction of 2 thus obtained gives 3,4-dihydroquinolin-2(lff)-ones (4), the present reaction provides a convenient method for synthesis of 4 from 1.
The bivoltine cricket locally known as 'Tambo-Koorogi' (Modicogryllus sp.) hibernates as a half-grown larva, and shows a developmental response to changing as well as stationary photoperiod. At 25 ~ C, larvae matured in about 7-10 weeks in continuous or 16 h daily light, but took 10-20 weeks or more in 14 h and shorter days. A day of 15 h exerted an intermediate effect, giving a development time of 7-17 weeks. However, an increase in daylength from 12 to 15 h in the early larval life prevented diapause, while a decrease from 15 to 12 h retarded development more than a constant 12 h day. Short-winged adults occurred only when the photophase was 15 h or shorter, and their frequency increased with decreased daylength. Although the short-winged form took longer to mature than the long-winged form under the same conditions of photoperiod, delayed growth was not always associated with brachypterism.
Tungstate-catalysed oxidation of 1,2,3,4-tetrahydroquinolines with hydrogen peroxide gives 1hyd roxy-2-0x0-I ,2,3,4-tetra hydroq u i no1 i nes highly efficiently.
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