BF₃-Et₂O-Mediated One-Pot Synthesis of Acetylchromans from Polyhydroxyacetophenones and Isoprene/Allyl Alcohol

Synthesis and Insight into the Structure–Activity Relationships of Chalcones as Antimalarial Agents

“…We wanted to study the cyclization effect of prenyl or geranyl group of chalcones; therefore, few chromanochalcones in which the C -prenyl or C -geranyl groups are involved in cyclization with phenolic hydroxyl group were synthesized. Initially, chromanochalcones 18 – 22 were prepared through a short and convenient route developed by us, which involves the one-pot synthesis of acetyl chromans 16 and 17 by carrying out a reaction between 1 and isoprene using BF 3 ·Et 2 O (Scheme ) and Claisen–Schmidt condensation of resultant chromans 16 and 17 with various substituted aromatic aldehydes. The chromanochalcones 25 and 26 were synthesized by pyridine-catalyzed condensation between 1 and citraldimethylacetal to provide the acetylchromene 23 .…”

“…Chromanochalcones 83 – 88 and chromenochalcones 90 – 100 which have hetero atoms in ring-A (Figure ) were synthesized using Claisen–Schmidt condensation from acetyl chromans 16 , 17 , 24 , and 82 and acetyl chromens 23 , 28 , and 89 , respectively, and various heteroarylaldehydes as shown in Scheme .…”

Highly Efficient and Selective Deprotection Method for Prenyl, Geranyl, and Phytyl Ethers and Esters Using Borontrifluoride–Etherate

“…Organic chemists have to some extent responded to these challenges to achieve selectivity in organic synthesis. During our drug discovery program on the synthesis of bioactive prenylated chalcones, [2][3][4][5][6] we observed a facile prenyl group deprotection of acetophenones under the influence of BF 3 Á OEt 2 . Deprotection attempts were also successful on geranyl and phytylated aromatic ethers using BF 3 Á OEt 2 , which prompted us to carry out further work on this reagent.…”

Synthesis of the Proposed Structure of Damaurone D and Evaluation of Its Anti-inflammatory Activity

“…This two-step procedure to obtain the chromane structure was more regioselective than previously described one-step reaction using isoprene. 20) In addition, microwave irradiation enhanced the reaction rate with a slightly improved chemical yield than the reflux conditions described in a previous study. 19) However, interestingly, chromene annulations of hydroxycoumaranone 5 to synthesize chromene 8 under microwave irradiation and reflux conditions afforded only a mixture of aldol adducts.…”