Studies On Tandem Cyclization Involving Substituted Aryl Isothiocyanate

Aryl isothiocyanate is an important intermediate in organic synthesis.It is easy to preparation and has a variety of chemical reactivity.Because of their high electrophilicity,aryl isothiocyanates are easily attacked by many nucleophiles to build carbon-carbon and carbon-heterobonds with important application value.In addition,due to the presence of terminal sulfur atoms,aryl isothiocyanates can also be used as nucleophiles and free radical acceptors,so substituted aryl isothiocyanates can be used to construct certain organic heterocyclic compounds with important functions,especially for the construction of certain functional bicyclic and polycyclic compounds.This paper is based on the related research of tandem reaction involving substituted aryl isothiocyanate,which is mainly divided into the following three aspects.Firstly,this paper develops an example of silver(I)catalyzed bicyclic cyclization of 5H-benzo[d]tetrazole[5,1-b][1,3]thiazine compound based on the tandem aryl isothiocyanate and sodium azide.In this reaction,sodium azide is used as a nucleophile to attack the aryl isothiocyanate fragment,and a[3+2]cycloaddition occurs,followed by a one-step nucleophilic attack in the molecule to obtain the target product.Studies have shown that the target product structure of the reaction is controlled by different substituents on the alkynyl group,resulting in the reaction undergoing different cyclization modes and the regioselective formation of six-membered or seven-membered ring addition methods.The silver-catalyzed tandem bicyclization proposed in this paper provides a simple and efficient new method for the construction of small molecule nitrogen and sulfur heterocyclic compounds.The reaction has the superiorities of simple operation,mild conditions and high yield.Secondly,this paper develops a new example of the tandem double cyclization of o-alkenylaryl isothiocyanate and propargylamine without transition metal catalysis to construct a new thiazolo[2,3-b]quinazoline derivative method.The reaction also went through a step of[3+2]cycloaddition,followed by a step of nucleophilic attack in the molecule,and the target product was obtained in a very high yield.This reaction constructs two new rings in one step,and obtains an extra-ring double bond that is not easy to preparation.The synthetic method has the advantages of high efficiency and environmental friendly,simple operation and wide application range of substrates.Thirdly,this paper develops a new method for the construction of phosphono-substituted benzothiazine compounds by the tandem reaction of o-alkynylaryl isothiocyanate and phosphono compounds catalyzed by inexpensive copper.The successful implementation of this method provides a new way for the formation of Csp~2-P bonds.and the reaction has the characteristics of simple operation,mild conditions,and higher yield.