General in situ trapping procedure

Benzo[c]furans (isobenzofurans) are very reactive but generally unstable dienes which are prepared in situ and trapped. The in ihu-generated isobenzo-furan 33 was trapped by cycloaddition reaction with bis(methyl (S)-lactyl) ester 34 to afford [32] optically active naphthols (Equation 2.12). The cycloaddition was carried out in the presence of a catalytic amount of glacial acetic acid and represents a facile one-pot procedure to synthesize substituted naphthols. 

H-Phosphinates 54 may also serve as precursors for phosphonamidates 56 (Scheme 18).l63 74 75] In the simplest procedure, a N-protected H-phosphinate 54 (produced, for example, by the Baylis procedure,156 see Section 10.10.1.2) is treated with a mixture of CC14, TEA, and the desired amino component. The H-phosphinates are converted in situ into phosphonochloridates 52, which are then trapped by the amine component. Sampson and Bartlett 761 reported improved yields when the H-phosphinate was first treated with bis-(trimethylsilyl)acetamide (BTMSA) to produce the trivalent species 55. They also noted that the reactions are generally cleaner when phosphinate ethyl esters are used instead of phosphinate methyl esters, presumably because the latter are more prone to nucleophilic demethylation. 

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