Sulfony limine

A fundamentally different approach to the synthesis of 3-pyrrolines is evidenced in the annulation in Eq. 13.50 [58]. Ethyl 2,3-butadienoate 150 reacts with N-sulfony-limine 151 in the presence of triphenylphosphine under very mild conditions to give JV-protected 3-pyrroline 152 in 90% yield. The mechanism that has been postulated is related to that of the Baylis-Hillman reaction. Michael addition of triphenylphosphine to the allenyl ester generates a zwitterion that combines with the imine to give 153 in a non-concerted process. This is followed by ring closure, proton exchange and expulsion of triphenylphosphine to give 152. This annulation is successful only for aromatic or cinnamyl imines [59]. 

A polystyrene-supported l,l -bi-2-naphthol phosphoric acid derivative (296) has been synthesised and applied in the enantioselective Friedel-Crafts reaction. The immohilised catalyst (296) has been found to be highly active and selective for the reaction of indoles (293) and sulfony-limines (294), and gave corresponding 3-indolylmethanamines (295) with high excellent enantioselectivities (up to 98% ee) (Scheme 79). Moreover, the recycling of (296) (14 cycles) was possible with no substantial loss in catal34ic performance. ... 

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See also in sourсe #XX -- [ , ]

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