Tandem Cyclization Reactions Of Ynamides For The Synthesis Of Organosulfur And Organoboron Heterocyclic Compounds

Element-organic chemistry is the scientific study of the B,Si,P,S and other non-metal-heteroatoms containing organic compounds,which is widely considered as one of the most influential branches of modern chemistry.Due to their unique chemical properties,element-organic compounds serve as an essential part in biological,medicinal,material and structural chemistry,and are broadly applicated in national defense,material science,pharmacology and energy fields.In this thesis,we combined ynamide chemistry with element-organic chemistry,and a series of organosulfur or organoboron compounds were successfully synthesized.Main contents of this thesis include the following four parts:In the first part,we introduced the synthesis and application of chiral organosulfur compounds as well as the construction of organoboron compounds by the insertion of B-H bonds,respectively.By summarizing the background and focusing on the limitations of above-mentioned fields,practical research objectives were proposed.In the second and third part,an efficient and catalyst-dependent cascade cyclization of sulfoxide-ynamides via[3,3]-sigmatropic rearrangement was developed,leading to the divergent and atom-economical synthesis of various valuable 1,6-benzothiazocines and 1,5-benzothiazepines in moderate to good yields with broad substrate scope.Importantly,the asymmetric synthesis of these medium-sized N,S-heterocycles has been achieved with excellent enantioselectivities via chirality-transfer strategy.In addition,preliminary investigation of chiral copper-catalyzed kinetic resolution of this cascade cyclization was also conducted with an acceptable result.Furthermore,the proposed mechanistic rationale for this catalyst-dependent chirality transfer was strongly supported by theoretical calculations.In the fourth part,an efficient copper-catalyzed cyclization of N-propargyl ynamides with borane adducts through B-H bond insertion was developed at first.This method allows practical and atom-economic synthesis of a series of valuable organoboron compounds in generally good yields with wide substrate scope and good functional group tolerance under mild reaction conditions.Importantly,this protocol expands the application of vinyl cations from C-H insertion to B-H insertion.Secondly,a new copper-catalyzed B-H bond insertion into α-imno copper carbenes generated from azide-ynamide cyclization was achieved,which was the first example of direct synthesis of α-boryl imines.