3380-61-8Relevant academic research and scientific papers
Bismuth(III) triflate catalyzed tandem esterification–Fries–oxa-Michael route to 4-chromanones
Meraz, Kevin,Gnanasekaran, Krishna Kumar,Thing, Rup,Bunce, Richard A.
supporting information, p. 5057 - 5061 (2016/11/02)
An efficient tandem reaction approach is described to prepare 4-chromanones from electron-rich phenols and 3,3-dimethylacrylic acid or trans-crotonic acid in boiling toluene using 20?mol?% bismuth(III) triflate as the catalyst. The reaction is also successful from the corresponding aryl esters of each of these acids under the same conditions. The procedure is convenient to perform, and 25–90% yields of products are realized following chromatography. A range of substrates is included (14 substrates for each acid) to help define the scope of the process. Additional experiments are reported, which confirm that the sequence of events involves (1) esterification, (2) Fries rearrangement and (3) oxa-Michael ring closure.
STUDIES ON THE SYNTHESIS OF PRECOCENES. THE PHOTO-FRIES REARRANGEMENT OF ESTERS OF α,β-UNSATURATED CARBOXYLIC ACIDS AND META-OXYGENATED PHENOLS
Miranda, Miguel A.,Primo, Jaime,Tormos, Rosa
, p. 673 - 682 (2007/10/02)
The photo-Fries rearrangement of a series of aryl esters of α,β-unsaturated carboxylic acids 1a,b and 2 has been investigated, in order to explore the possibilities of this reaction as a key step in the synthesis of precocenes and related compounds.In all cases, the photolysis in hexane does not lead to any observable transformation, but in the presence of potassium carbonate takes place a migration of the acyl group to the two ortho-positions.Additionally, trans-cis photoisomerization occurs with the trans-butenoate 1b.The resulting o-hydroxyketones 4a, 4b, 4c, 5a, 5b, 5c, and 8 are easily and efficiently cyclized to the corresponding 4-chromanones 6a, 6b, 7a, 7b, and 9.A second photo-rearrangement is observed in the case of 9, although the yield is low, due to deactivation by the carbonyl group.Cyclization of 10 gives rise to the tricyclic dichromanone 11.Compounds 6a and 11 are reduced and subsequently dehydrated by known procedures to afford the active chromenes 3 and 12.
Synthesis of 13-Aza-18-nor-7-methyl-17-oxo-6-oxa-estra-1,3,5(10),9(11)-tetraene 3-Methyl Ether and 13-Aza-18-nor-7-methyl-17-oxo-6-thia-estra-1,3,5(10),9(11)-tetraene 3-Methyl Ether
Trehan, I. R.,Farwaha, Rajeev,Sharma, R. K.,Kaul, R. L.
, p. 87 - 89 (2007/10/02)
Modified Wittig reaction of chromanone (Ia) and thiochromanone (Ib) with triethylphosphonoacetate provides the conjugated esters (IIa and IIb) which on LAH reduction furnish the allylic alcohols (IIIa) and (IIIb) respectively.Alkylation of succinimide with IIIa and IIIb in the presence of triphenylphosphine and diethyl azodicarboxylate gives the seco-steroids (IVa) and (IVb) respectively.Reduction of these secosteroids with sodium borohydride at pH 3 results in the generation of ethoxyamides (Va and Vb) which on subsequent cyclization in the presence of PTS yield the title compounds (VIa) and (VIb) respectively.
