Unusual nitrogen based heterocycles via allenic intermediates from the reaction of propargyl alcohols with P(III) substrates

The apparently simple reaction of the P(III) precursors [(RNH)P(μ-N-t-Bu)₂PY] (Y=NH-t-Bu, Cl), (OCH₂CMe₂CH₂O)PCl, and Ph₂PCl with functionalized propargyl alcohols is examined. In most cases, the final products are not the expected allenes but several previously unpredicted structural motifs, such as substituted oxazabenzocycloheptenones, indolinones, and fused heterocycles as revealed by X-ray crystallography. Mechanistic aspects of these novel reactions, as well as possible utility and the structural chemistry of the products are also discussed. The P–C or P–N bond cleavage of many of these compounds led to phosphorus-free 2-substituted indoles, quinolinones, and tetrahydroacridine.