Synthesis Of 6H-benzo[C] Chromene And Natural Products Cannabinol,Blennolide C And Parnafungin A

The construction of aryl-aryl C-C bonds is one of the important tools for modern organic synthesis.In this thesis,the synthesis of 6H-benzo[c]chromene was accomplished by intramolecular dehydrogenation of two aryl C-H bonds catalyzed by palladium.In addition,natural product cannabinol was synthesized efficiently with this method.Studies on the asymmetric synthesis of natural products blennolide C and parnafungin A have also been performed.This dissertation is mainly divided into three chapters:Chapter 1.Progress in synthesis of biaryl compoundsBiaryls are ubiquitous structural motifs in natural products,pharmaceuticals,agrochemicals,and functional materials.The development of efficient methods to access biaryl compounds has accordingly attracted significant attention of synthetic chemists.Many outstanding researches resulted in important named reactions such as Suzuki,Stille,Hiyama,and Negishi couplings.Classically,biaryls are achieved by cross-couplings of organometallic aryls with aryl halides(C-X/C-M).In the past decade,the direct C-H/C-H catalytic dehydrogenative cross-coupling(CDC)between two arenes,as an ideal approach by improving step and atom economy and reducing waste,has been greatly developed.This charter reviewed recent progress in CDC reactions for biaryl bond formation.Chapter 2.Synthesis of 6H-benzo[c]chromenes via palladium-catalyzed intramolecular dehydrogenative coupling6H-Benzo[c]chromenes are an important class of organic compounds present in numerous natural products and bioactive molecules,Considering the potential utilities of these molecules,the synthesis of 6H-benzo[c]chromenes remains of long-standing interest in organic chemistry.In this charter,at first the synthesis of 6H-benzo[c]chromenes in recent years was summarized briefly.Then,as first part of our researches,a palladium-catalyzed intramolecular C-H/C-H coupling between two simple arenes to construct 6H-benzo[c]chromenes was reported for the first time.The approach is featured by broad substrate scope,good tolerance of functional groups,and using molecular oxygen as terminal oxidant.Notably,the products are useful synthetic intermediates,as clearly demonstrated by efficient total synthesis of natural product cannabinol with simple operation in 55%overall yield from commercially available materials.Chapter 3.Studies on synthesis of tetrahydroxanthones:blennolide C and parnafungin ATetrahydroxanthones exist in nature widely.Due to their broad biological activities and unique synthetic challenge,The synthesis of these compounds attracted considerable interest of chemists.To date,asymmetric synthesis blennolide C is rarely reported.The synthesis of prnafungin A is only limited in the model study.This chapter began with a summary of the previous synthesis work,followed by our studies on the synthesis of blennolide C,as well as parnafungin A.In the synthesis of blennolide C,the first proposed routes(9 steps)was eventually failed,and then we implemented the second route,employing opening epoxy ring,hydroxyl selective protection,nucleophilic addition of aromatic lithium to aldehyde as key steps to synthesize the key intermediates of blennolide C via 14 linear steps.Meanwhile,the key intermediates for the synthesis of natural product parnafungin A were achieved by 9 steps.