The cycloaddition reaction of 3,4-dimethyl-1-thio-1-phenylphosphole with tropone

3,4-Dimethyl-1-thio-1-phenylphosphole reacts, under elevated temperatures, with tropone to give two 4+2] isomeric adducts: Endo-syn-5,6-dimethyl-3-thio-3-phenyl-3-phosphatricyclo 5.3.2.0^2,6]dodec-4,8,11-trien-10-one (1) and Endo-anti-5,6-dimethyl-3-thio-3-phenyl-3-phosphatricyclo5.3.2.0^2,6]dodec-4,9,11-trien-8-one (2). In addition to the endo-exo,syn-anti relationship the phosphorus configuration in 1, 2 and some derivatives was also elucidated by means of NMR-shift reagents and ²J_PH coupling constants.