During the course of our studies on a-activated cross conjugated cycloalkenone systems in organic synthesis, we have serendipitously discovered that compound 2, obtained through 1,4-conjugate addition of l-(trimethylsilyl)-l-butyn-4-yl magnesium chloride to a-cyano cyclohexenone 1, could undergo autoxidative annulation upon exposure to air and light to afford cyclic products 3 and 4, respectively (Figure 1). To optimize reaction conditions, reaction parameters, including solvents, bases and time, were systematically varied and monitored. As a result, the system (pyridine (catalyst)/02 (1 atm)/rt) is found to be the method of choice to effect the observed autoxidative reaction. On the basis of this newly developed protocol, a variety of highly functionalized bicyclic frameworks can be effectively constructed in moderate to good yields as illustrated in Scheme 1.
