Behaviour of ɑ-carbethoxy radical generated from the ester of N-hydroxy-2-thiopyridone

533-53

Microwave assisted solvent free synthesis of 1,3-diphenylpropenones

<p>Abstract</p> <p>Background</p> <p>1,3-Diphenylpropenones (chalcones) are well known for their diverse array of bioactivities. Hydroxyl group substituted chalcones are the main precursor in the synthesis of flavonoids. Till date various methods have been developed for the synthesis of these very interesting molecules. Continuing our efforts for the development of simple, eco-friendly and cost-effective methodologies, we report here a solvent free condensation of aryl ketones and aldehydes using iodine impregnated alumina under microwave activation. This new protocol has been applied to a variety of substituted aryl carbonyls with excellent yield of substituted 1,3-diphenylpropenones.</p> <p>Results</p> <p>Differently substituted chalcones were synthesized using iodine impregnated neutral alumina as catalyst in 79-95% yield in less than 2 minutes time under microwave activation without using any solvent. The reaction was studied under different catalytic conditions and it was found that molecular iodine supported over neutral alumina gives the best yield. The otherwise difficult single step condensation of hydroxy substituted aryl carbonyls is an attractive feature of this protocol to obtain polyhydroxychalcones in excellent yields. In order to find out the general applicability of this new endeavor it was successfully applied for the synthesis of 15 different chalcones including highly bioactive prenylated hydroxychalcone xanthohumol.</p> <p>Conclusion</p> <p>A new, simple and solvent free method was developed for the synthesis of substituted chalcones in environmentally benign way. The mild reaction conditions, easy work-up, clean reaction profiles render this approach as an interesting alternative to the existing methods.</p

Studies on ambiphilic radicals generated from the ester of <i>N </i>-hydroxy-2- <span style="font-size:14.0pt;line-height:115%;font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";color:#181818;mso-ansi-language:EN-IN; mso-fareast-language:EN-US;mso-bidi-language:HI" lang="EN-IN">thiopyridone^†1</span>

592-596Seven different α-carbethoxyalkyl radicals have been generated from Barton esters and their behaviour towards different olefins have been studied to show their philicity

Behaviour of α-carbethoxy radical generated from the ester of <i>N</i>-hydroxy-2-thiopyridone

533-535Studies on the behaviour of α-carbethoxy radical generated from the ester of N-hydroxy-2-thiopyridone is described

Sodium borohydride-iodine, an efficient reagent for reductive amination of aromatic aldehydes

1970-1971Reactions of aromatic aldehydes with primary amines give the corresponding secondary amines in the presence of iodine and sodium borohydride in methanol

Reductive removal of the tert-hydroxy group in α,β-unsaturated γ-tert-hydroxyketones with chlorotrimethylsilane-sodium iodide. An alternative to zinc-acetic acid reduction

Chlorotrimethylsilane-sodium iodide effects reductive removal of the tert-hydroxy group in the α, β-unsaturated γ-tert-hydroxyketones (1), (3), (5), and (7)

Microwave promoted selective preparation of acetals and esters from aldehydes

1032-1038A new selective method of acetalization of aldehydes and cyclic ketones with 1,2-diols or alcohols catalyzed by iodine under microwave irradiation is reported. Depending upon the reaction conditions further oxidation of the arylidene acetals takes place in the system leading to the formation of products like iodoester 2 and hydroxy esters 3, 4 and 5. Both unsubstituted (1a) and substituted arylidene acetal with electron releasing group (1d) give high yield of iodoester 2 (70-80%) whereas the arylidene acetal substituted with an electron withdrawing group such as NO2 (1b) gives a low yield of the corresponding iodoester (2b, 25%)