Study On Synthesis Of ?-lactam Compounds By UV Light

?-lactam,a four membered ring,was found to be the key structure of many antibiotics for clinical use,besides,it was served as an critical synthon for the preparation of amino acids,alkaloids and taxoids.As is well-known,the ?-lactam ring was always identified as the core of valuable structural units,pharmacologically active molecules and bioactive natural/non-natural compounds.Thus,numerous efforts have been devoted to its preparation.However,as far as we know,reported methods on the constructing of ?-lactam ring often suffered from many disadvantages,such as harsh conditions,tedious multi-step.Despite the starting material is inexpensive and available,expensive metals are always used in the cyclization process.For this reason,develop a green,environmentally friendly and simple synthetic method was of very important economic and social significance.In this paper,we explored an intramolecular cyclization reaction,which was induced by ultraviolet light irradiation,by using methacrylamides as substrates.Such a protocol provided a novel and convenient way to synthesis of compounds with the structure of ?-lactam.Besides,N-allyl-N-(p-toluenesulfonyl)methacrylamide was chosed to screen the reaction conditions.And finally,the optimal conditions were determined by use methanol as solvent,quartz tube as container,300 nm ultraviolet light as light source,additionally,the optimal substrate concentration was 0.005 mmol/mL.Under the standard conditions,the photochemical behavior of 24 methacryloyl benzenesulfonamide compounds were investigated,and only 18 of the corresponding products could be isolated with moderate yields.Based on the previous reports,a plausible mechanism was proposed.Under the irradiation of UV light,the ? bond of C-H,which was adjacent to the N atom,in the allyl or isopropyl group was excited and release a hydrgen atom via a homolysis process.Subsequently,1,5-hydrogen migration occurred.Then the two generated radical coupled with each other and gave the final four-membered ?-lactam derivatives.