Studies On The Cascade Reactions Of Phosphinyl Allenes With N-tosylhydrazones Or Disulfides

Allenes are a class of unique compounds with a 1,2-diene moiety and widely exist in natural products and bioactive molecules.Allenes have been studied showing novel patterns for construction of various molecules with excellent region-and stereoselectivity via its unique reactivity.Moreover,allenes have been applied as key intermidiates in the synthesis of complex natural products and molecules.Therefore,allenes have received much attention due to its unique structure and chemical properties.Based on this,the work focused on the studies on the cascade reactions of phosphinyl allenes with N-tosylhydrazones or disulfides.This dissertation includes the following three parts:1?the cascade reactions of palladium catalyzed N-tosylhydrazones and phosphinyl allenesDue to lack of recognition in the early stage,the chemical development of Dendralenes,discrete acyclic cross-conjugated olefins,lags behind,especially the synthesis of multi-substituted Dendralenes.We develop a palladium-catalyzed cascade reactions of phosphinyl allenes with N-tosylhydrazones leading to novel phosphinyl[3]Dendralenes.Then the optimum reaction conditions were screened out with solvents,base,catalysts and additives investigated.The yield was greatly improved when t-BuCOONa was used as an additive.According to a large number of studies on palladium-catalyzed allenes and N-tosylhydrazones combined with previous research of phosphinyl allenes by our group,a plausible mechanism was propose:The carbene species decomposed from N-tosylhydrazones is captured in situ by a ?-allyl-palladium species decomposed from phosphinyl allenes to form a ?-allyl-palladium carbine species.The intermediates with the diazo compounds toward metal insertion,transfer metallization,?-hydride elimination,and then get coupling product,Single crystal structure revealed the dimensional orientation of multiple double bonds in phosphinyl[3]Dendralenes.2?the alkylation and cyclopropanation cascade reactions of N-tosylhydrazones and phosphinyl allenes with metal-free conditionsCyclopropane with high tension is a very important class of organic synthesis intermediates.Cyclopropanes easily been available and having good reactivity are frequently employed as versatile building blocks in organic syntheses.Cyclopropane derivatives with electron-donating or-withdrawing groups are involved in their reactions to make polar processes more favorable.Ring cleavage or ring enlargement may then occur under relatively mild conditions because of the electronic effect Different from previous research of palladium-catalyzed cascade reactions of phosphinyl allenes with N-tosylhydrazones leading to novel phosphinyl[3]Dendralenes,an alkynylcyclopropane derivatives were got from trisubstituted phosphinyl allenes.Then screening out the optimum reaction conditions,it only requires a catalytic amount of 1,10-Phen·H2O as an additive without transition metal catalyst,expensive ligands and stoichiometric oxidants.This cascade reaction of phosphinyl allenes with N-tosylhydrazones is setreoselective and shows a broad functional group tolerance and good yields.3?the cascade reactions of visible-light-driven aryl disulfides and phosphinyl allenesThe synthesis methods of alkenyl sulfides have been developed and innovated by scientists due to the widely application of the unique chemical structure in natural products and bioactive molecules.Typically,the most powerful methods for constructing alkenyl sulfides rely on the thiolation of alkynes and transition-metal-catalyzed crosscoupling of vinyl precursors with sulfur sources.Given the increasing demands in green and sustainable chemistry,this dissertation develops a visible-light-driven cascade reaction of phosphinyl allenes with disulfides leading to novel phosphinyl alkenyl sulfides as wonderful strategies for C(sp2)-S formations.The mechanistic studies clearly support the photoredox cleavage of an ?-allenylic C-O bond to initiate radical intermediates instead of a sulfur radical.The reactions exhibited many advantages including mild conditions,eco-benign procedures,and good functional group compatibility.Under visible light irradiation,successive cleavage of an a-allenylic C-O bond and alkenyl C-S formation were involved,delivering a series of novel S,P-bifunctionalized butadienes with moderate to excellent yields.It is worthy to mention that,owing to a combined effect of the stabilization of electron-deficient groups to radical intermediates and ?-? stacking between the aromatic substitutions and P(O)Ph2 moiety,E isomers were obtained exclusively.