[a] Reactions were carried out on 0.1 mmol scale (0.03 M in MeCN). Yield was determined by 1 H NMR analysis of the crude reaction mixture using 1,3,5-trimethoxybenzene as an internal standard. Isolated yields are quoted in parentheses for reactions conducted on 0.3 mmol scale. [b] 0.1 M in MeCN. CHD = cyclohexadiene. TMP = tetramethylpiperidine.