Benzenes Baylis—Hillman adducts

Remarkably, thermolysis of the Baylis-Hillman adducts 311 (R1 = alkyl or aryl Rz = Ac, CN, CC Me) in toluene at 210 °C in a sealed tube gave stereoselectively the cyclized product (+)-312, which included incorporation of the elements of the solvent and, when Rz = Ac, a single isomer was obtained (Equation 33). The yields were moderate (37-56%) and when RZ = CN and C02Me some racemization occurred. Similar results were obtained when either p-xylene or mesitylene was used but no reaction occurred when chlorobenzene or anisole was used. Unsaturated rings are obtained in similar yields and stereoselectivity if the N-substituent is an alkyne. In addition, benzene thiol reacted in boiling benzene in the presence of AIBN to give 313, which on ozonolysis yielded the cyclic ketones 314 ( = 1-3) in 52-70% yield <2001JOC1612>. 

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