New Addition and Cyclization Reactions Involving Phosphorus Based Allenes

Allenylphosphonates and allenylphosphine oxides constitute an important subclass of allenes that show versatile reactivity. An important advantage of phosphorus-based allenes is that the reaction can be very conveniently... [ view full abstract ]

Allenylphosphonates and allenylphosphine oxides constitute an important subclass of allenes that show versatile reactivity. An important advantage of phosphorus-based allenes is that the reaction can be very conveniently monitored by ³¹P NMR spectroscopy, since a single signal for each of the products is often observed. This talk will focus on some of our contributions to the chemistry of allenylphosphonates and allenylphosphine oxides that relate to the synthesis of phosphorus-based benzofurans, isocoumarins, isoquinolones, cyclopenta[c]quinolines etc.

Two representative reactions are highlighted below. In the first reaction, a phosphonoisoquinoline is formed by the reaction of an allenylphosphonate with 2-iodo-substituted imine. The reaction involves elimination of isobutylene as well as HI while leading to the isoquinoline ring. In the second reaction shown below, instead of cyclization using the aldehyde functionality also, a phenol addition product is formed, that possesses residual aldehyde functionality.

Acknowledgements: We thank DST (New Delhi; J C Bose Fellowship) and CSIR (New Delhi) for funding.

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