Synthesis of New Tricyclic Phosphines and Phosphinites by Intramolecular Diels−Alder Reactions of Trivalent Phospholes

Phospholes bearing an allyl-X substituent at
phosphorus tend to undergo an intramolecular Diels−Alder
cycloaddition (IMDA) leading to the corresponding tricyclic
derivative. When X = O or NR, the IMDA easily takes place
at room temperature. When X = CH2, the IMDA slowly takes
place around 110−140 °C, as a function to the substitution
pattern of the dienic system. Two tricyclic derivatives (X =
O and CH2) have been characterized by X-ray crystal
structure analysis of the P-sulfides.