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Regioselectivity in hetero Diels–Alder reactions can be observed in a simple reaction between a nonsymmetrical heterodiene and an unsymmetrical heterodienophile. A 9 h and easy to implement laboratory experiment is described, in which students can observe the regioselectivity of inverse “electron-demand” hetero Diels–Alder reactions of an azoalkene with furan or 2,3-dihydrofuran acting as dienophile. This experiment combines synthesis, structural analysis (IR spectroscopy and NMR spectroscopy), and dry- and vacuum-flash isolation methods.

The synthesis of new 3‐tetrazolyl‐1,4,5,6‐tetrahydropyridazines by Diels–Alder reactions of ethyl 3‐(tetrazol‐5‐yl)‐1,2‐diaza‐1,3‐butadiene‐1‐carboxylates is reported. These 1,2‐diaza‐1,3‐dienes reacted with electron‐rich heterocycles, nucleophilic olefins and cumulenes, as well as with electron‐deficient dienophiles, to give the target compounds regioselectively. Computational studies corroborated the rationalization of the observed reactivity and selectivity.

X-Ray structure determinations on a variety of aryloxytetrazoles 1 and aryloxypseudosaccharins 4 have shown that the central C&z.sbd6;O&z.sbd6;C ether linkage is remarkable in having one very long C&z.sbd6;O bond and one very short one. The central C&z.sbd6;O&z.sbd6;C bond angle is close to 120°. The implications of these effects on the reactivity of compounds 1 and 4 towards catalytic hydrogenolysis or cross-coupling are explored.

Reasons are given for the formation of two different products from the chlorination of saccharin with phosphorus pentachloride: initially 2-chlorosulfonylcyanobenzene is formed which, under appropriate conditions, cyclises to give 3-chloro-1,2-benzisothiazole 1,1-dioxide, an important derivatising agent for alcohols.

Botanical origin, physicochemical properties (ash, colour, diastase activity, electrical conductivity (EC), hydroxymethylfurfural (HMF), moisture, optical rotation (OP), pH, reducing sugars, total acidity, total soluble solids, and water activity), bioactive compounds (BC), and antioxidant activity obtained from strawberry tree honey from South Portugal were investigated. Results showed that the pollen analysis and physicochemical parameters were found within to meet international honey specifications. Significant differences (P<0.05) in results of ash content, EC, HMF, OP and colour when were compared with analogous famous Italian honey (Sardinia island). For BC, total phenolic and total flavonoid content were 94.47 mg gallic acid/100 g and 5.33 mg quercetin/100 g, respectively. Concerning Portuguese honey, it was also found that radical scavenging activity (DPPH assay) was 43.46% and antioxidant activity was 18.85 mg ascorbic acid equivalent/100 g and 9.92 mg quercetin equivalent/100 g. These results confirmed that Portuguese strawberry tree honey has the highest antioxidant activity, when compared with other kinds of honey. This complete report demonstrates advantages and can help to promote consumption and shown their benefical properties (e.g., antioxidant); which will may increase the commercial value.

3-Allyloxy-1,2-benzisothiazole 1,1-dioxides 4isomerize thermally to give [3,3]- and [1,3]-products 5, 6of sigmatropic shift, of which the former reacts further to give solely the [1,3]-isomer.

3-Allyloxy-1,2-benzisothiazole 1,1-dioxides 4 isomerize thermally to give [3,3]- and [1,3]-products 5, 6 of sigmatropic shift, of which the former reacts further to give solely the [1,3]-isomer.

3-Allyloxy-1,2-benzisothiazole 1,1-dioxides 4 isomerize thermally to give [3,3]- and [1,3]-products 5, 6 of sigmatropic shift, of which the former reacts further to give solely the [1,3]-isomer.

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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.