Synthetic Study Of The Analogue Of Conidiogenone

This thesis mainly focused on the synthesis of analogue 6 of conidiogenone.Two proposed synthetic pathways are described(Scheme 4,5).The key step of the routes is a Diels-Alder reaction between 2,3-dicyanhydroquinone(1) and 1-vinylcyclohex-1-ene(9) in the presence of Pb304 to form the skeleton of the tricyclic conjugated enone 8 which is an important intermediate.Product 11 was prepared by the reduction of carbon-carbon double bond of 8,and 11 is a common intermediate in two routes.In Route 1,two methyl groups of 12 were designed to be converted synchronously from the a-cyano ketone of 11 with a reductant and LiCH3.However,we failed to obtain compound 12, but got aromatized product 34.Thus,Route 1 was not able to continue.In Route 2,the methyl groups of 6 could be developed from cyanos by different pathways individually(Scheme 5).In this thesis,we have completed the protection of one ketone group of 11,and further synthesis is currently under investigation.During the course of synthetic study of the analogue of conidiogenone,we have developed a new synthetic method and found a novel reaction which has not be reported.(1) We have developed an efficient general method for one-pot reaction of hydroquinone derivatives and dienes under the system of Pb304 in THF with small amount of TFA. In this procedure,the role of Pb₃O₄ is not only as an efficient oxidant for the generation of quinone compounds in situ,but also as an excellent catalyst for the following Diels-Alder reaction.The dual roles of Pb₃O₄ in one-pot to our knowledge have not been reported.(2) An unusual reaction for lactone was observed during the protection ofα-cyano ketone under pyridine-pyridinium salt at reflux.The reaction probably involves the hydrolysis of cyano into intermediate of amide or acid,which further reacts with the newly formed ketal to give lactone. Detailed mechanism is currently under investigation.