Studies On Total Synthesis Of Alkloid Rubrolone And Sequiterpenes Natural Products

This thesis aims at studies on the total syntheses of complex alkaloid Rubrolone aglycon and natural sesquiterpenes.To exploit new building blocks for functional materials,the Rhodium(Ⅰ)-catalyzed synthesis of aryltriethoxysilanes from arenediazonium tosylate salts was also investigated.The thesis consists of the following sections:Foreword:Brief introduction on the research background,scientific aim and significance of the investigations.PartⅠ:Total Synthesis of Rubrolone AglyconStarting from resorcinol,quinol and ethyl 3-oxohexanoate,we attempted two strategies for the synthesis of complex alkaloid Rubrolone Aglycon.Via methylation, Sandmeyer reaction,borication reaction,and pyridine synthesis,we achieved the synthesis of two key sections for Suzuki cross-coupling reaction.After a series of attempts,the desired Suzuki coupling was successfully carried out.Thereafter,we tried different methods for the preparation of diazoketone,including Arndt-Eistert reaction,Foster reaction and so on.Eventually,we were able to synthesize the diazoketone via diazo transfer reaction and construct the skeleton of Rubrolone aglycon after a Rhodium(Ⅱ) catalyzed Buchner reaction.PartⅡ:Total Syntheses of Humulane- and Bisabolane-type Natural Products.1.Starting from geranial aldehyde,via zinc-dust-catalyzed coupling,protecting sensitive functional group,Riley oxidation and addition with the olefin,we successfully obtained the precursor of RCM reaction.Some unsuccessful attempts of RCM reaction were explored to construct the 11-membered ring of humulane sesquiterpene.2.New synthetic strategy was proposed to redeem the failure of synthesizing Mitissimol A via RCM reaction.Starting from the aldehyde obtained in route 1(vide supra),β-oxo-carbonyl compound was obtained via addition reaction to methyl phosphate methylene followed by oxidation.The terminal product was synthesized via a Horner-Wadsworth-Emmons reaction with many attempts,through which the first total synthesis of Mitissimol A was eventually achieved.3.The first asymmetric total synthesis of natural 3,4-epoxybisabola-7(14),10-dien-2-one from(-)-carvone was performed.PartⅢ:Rhodium(Ⅰ)-Catalyzed Synthesis of Aryltriethoxysilanes from Arene- diazonium Tosylate Salts with TriethoxysilaneAn efficient method for preparation of aryltriethoxysilanes from arenediazonium tosylate salts has been developed with good yields during a two-step process in one-pot,which expands the substrates of rhodium-catalyzed silylation from iodides, bromides and triflates to diazonium salts.A new method for hydrodediazoniation has been explored as well.PartⅣ:Review on the Synthesis of Diazocarbonyl CompoundsA mini-review on the preparation of diazocarbonyl compounds was constructed according to the reaction's type,mechanism,and applications.Nearly all the methods to prepare diazocarbonyl compounds(e.g.diazoketone and diazoester) are covered with the time span from 1883,when the first diazoester was synthesized,to 2008.