tert-butyl substituent as a regiodirecting and novel C-H protecting group in cyclobutenedione-based benzannulation chemistry

2-Unsubstituted hydroquinone monoacetates, quinones, and 3-unsubstituted quinolizinones were synthesized in moderate to high yields via tert-butyl and trimethylsilyl substituted cyclobutenediones. The addition of unsaturated carbon nucleophiles proceeded regiospecifically at the carbonyl group most distant from the tert-butyl or trimethylsilyl substituent. Thermolysis of the adducts, followed by treatment under acidic conditions to remove the tert-butyl and trimethylsilyl groups in good overall yields, provided access to a variety of "less-substituted" hydroquinone monoacetates, quinones, and quinolizinones. Of the two systems, the tert-butyl-substituted cyclobutenediones proved the most useful.