Oppenauer's oxidation by paraformaldehyde of piperonyl alcohol to heliotropine

Isomerization of Allylbenzenes

“…Because safrole 6 is mostly obtained from plant material, there has been concern that unsustainable harvesting practices have resulted in deforestation, particularly in developing countries. In addition to these ecological concerns, the rising price of safrole 6 has resulted in alternative synthetic approaches to 3,4-methylenedioxybenzaldehyde 104 being investigated (in this regard, also see the section detailing with the use of solid bases, section ). , …”

“…In addition to these ecological concerns, the rising price of safrole 6 has resulted in alternative synthetic approaches to 3,4-methylenedioxybenzaldehyde 104 being investigated (in this regard, also see the section detailing with the use of solid bases, section 4.4). 242,243 Rabinovitz and Sasson reported a protocol that resulted in isomerization of allylbenzene 3 into trans-and cis-1propenylbenzenes 4 and 90, respectively (Scheme 21), which involved use of hydroxide ions under liquid−liquid PTC conditions with tetrabutylammonium bromide (TBAB) as catalyst. 205,206 The authors mentioned that the reactions were believed to proceed through a "hydroxide extraction mechanism", as determined by a number of physical organic chemistry experiments.…”

Further Steps of Zeolites Toward Industrial Applications

“…Monomeric tetrahedrally coordinated surface tungstate species responsible for the metathesis activity were formed via the interaction with Brönsted acid sites of HY zeolite. A new environment-friendly synthesis of hydroxyphenylalkylketones was developed based on the use of a commercial pentasil-type zeolite ensuring both the high conversion of phenylacetate and the high selectivity toward ortho-hydroxyacetophenone [152]. The best catalyst demonstrates the 2-butene conversion close to the thermodynamic equilibrium value (∼64%) at 453 K. The catalysts are bifunctional [148]: they catalyze first isomerization of 1-butene to 2-butene and then cross-metathesis between 1-butene and 2-butene to produce propene and 2-pentene.…”

Examples of heterogeneous catalytic processes for fine chemistry

“…Thus, an interesting alternative may be Oppenauer's oxidation, which can be performed under safe and mild reaction conditions using either homogeneous or heterogeneous catalysts, View Online synthesis of HEL by Oppenauer's oxidation of the corresponding PAL using widely available and inexpensive commercial PFA as the hydrogen acceptor. 109,110 Among the heterogeneous catalysts studied (commercial ZrO 2 and calcined HT compounds), the best initial results were obtained by using commercial zirconia-type catalysts, with high yields being obtained regardless of the catalyst amount and reagent concentration, although these catalysts cannot be regenerated. Calcined Mg/Al commercial HT phases (by Sasol D and Süd-Chemie D) showed not only good catalytic results (having only a lower reaction rate than zirconia-type examples), but also an almost complete recovery of the initial activity after calcination at 823 K for 6 h ( Fig.…”