Pinacol, photochemical formation

Dehydroifenatiun. I>iethyl azodicarboxylme has been shown lo elt eci photochemical dehydrogenation of isopropanol to pinacol" and of cyclohexunol lo cyclohexanone. Actually the reagent eifects nonphotochemical oxidation of alcohols, mercaptans, anilines, and hydrazobenzenes with formation of diethyl hydrazinodicarboxylate. ... 

Similar observations have been made during a study on the formation of crowno-phanes such as 14 (Scheme 9-8) which proceed smoothly even in rather concentrated solutions [19]. In this particular case, photochemical control experiments provide strong evidence that the titanium mediated process benefits from a significant template effect. Whereas the photoinduced intramolecular pinacolization of diketone 11 to diol 12 in 0.002 M solution is rather inefficient (=29%) [20], treatment of the same substrate with... 

Jensen and coworkers [25] demonstrated the photochemical synthesis of benzo-pinacol (Scheme 6.9) within a sUicon/quartz microreactor (channel dimensions 500 pm wide x 250 pm deep), which enabled UV light to pass through the quartz layer and irradiate the reaction mixture contained within the microchannel network. Employing on-line UV analysis, they were able to assess the reaction progress rapidly and with ease. Preliminary investigations conducted at flow rates of >10.0 pi min showed no benzopinacol formation. Only recovery of the unreacted starting materials benzophenone and 2-propanol was observed. By reducing the flow rate to... 

Chromium(v) is also detected in the course of oxidation of ethylene glycol by dichromate. The e.s.r. spectrum is consistent with a bis-complex (4) and its formation may be enhanced photochemically. A similar result is reported in the photochemical oxidation of pinacol by dichromate. ... 

---