Synthesis Of 2,7-Dioxabicyclo [2.2.1] Heptan-3-one Derivatives Via Sulfa-michael Addition/Cyclization Tandem Reactions

Organosulfur compounds with ring structure are widely used in the field of pharmaceutical chemistry,agricultural chemistry and materials chemistry.And they are also important biologically active groups in many natural products.The construction of cyclic organosulfur compounds with various structures is of great significance for the synthesis and modification of related biologically active compounds.Meanwhile,cyclic organosulfur compounds can also serve as useful synthetic scaffolds to a diverse array of building blocks,which are important intermediates in organic synthesis.Therefore,it is of great significance for the construction of cyclic organosulfur compounds.The tandem cyclization reactions triggered by sulfa-Michael addition can be used to prepare cyclic organosulfur compounds bearing stereocenters efficiently and stereoselectively in an atom-economic fashion.The isomerization of O-acyl hemithioacetal is an atom-economical method for synthesizing thioester compounds.We have demonstrated a practical tandem sequence to prepare α-hydroxy allylic thioesters by the combination of a Lewis base-catalyzed allylic alkylation of MBH adducts with a basepromoted hemithioacetal isomerization.The resulting allylic thioesters can serve as valuable scaffolds to undergo a stereoselective intramolecular cyclization to deliver cyclic organosulfur compounds.The main contents are as follows:1.We have developed a diastereoselective method for the preparation of 2,7-dioxabicyclo [2.2.1] heptan-3-one derivatives bearing sulfur moiety from allylsubstituted sulfur esters through a catalytic sulfa-Michael addition triggered tandem cyclization sequence under the mild reaction conditions.The products can be readily prepared in high yields with moderate to excellent diastereoselectivities.2.We have investigated the enantioselective synthesis of α-hydroxy ester allyl thioester compounds via O-acyl hemithioacetal isomerization/allyl alkylation reaction by using chiral Lewis base.The corresponding products can be obtained with moderate yields and enantioselectivities.Further investigations of this transformation are being carried out in our laboratory.