Cyclodiphosphazanes as synthetic probes: P-C/P-N bond formation from the reaction with functionalized propargyl alcohols and N-hydroxy substrates

Abstract

Phosphano-indoles were synthesized in a fairly straightforward route from the reaction of simple cyclodiphosphazanes [XP(μ-N-t-Bu)2PY] [X = Y = NH-t-Bu (1a); X = Y = NH-i-Pr (1b)] with o-aminophenyl functionalized propargyl alcohols. The reaction occurs via an allene intermediate formed by P III-O-C → P V(O)-C rearrangement, followed by cyclization utilizing the central allenic carbon and the -NH2 functionality. In a similar way, cyclodiphosphazanes [XP(μ-N-t-Bu)2PY] [X = Y = Cl (1c); X = Cl, Y = NH-t-Bu (1d)] have been treated with N-hydroxy substrates to obtain novel P III-O-N → P V(O)-N rearranged products. X-ray structures of the four products, 2-(1-phenyl-ethyl)-3-[(t-Bu)NH)P(μ-N-t-Bu)2P(O)]-indole [14], cis-{[-C(=O)-C6 H 4-C(=O)-]-N-P(=O)-N-t-Bu}2 [cis-18], trans-{[-C(=O)-C6 H 4-C(=O)-]-N-P(=O)-N-t-Bu}2 [trans-18] and cis-[(t-BuNH)P(μ-N- t-Bu)2P(=O)-N{ -C(=O)-CH2-CH2-C(=O)-}] [cis- 19] are also reported.