The Pd-catalyzed coupling of N-allyl sulfamides with aryl and alkenyl triflates to afford cyclic sulfamide products is described. In contrast to other known Pd-catalyzed alkene carboamination reactions, these transformations may be selectively induced to occur by way of either anti- or syn-aminopalladation mechanistic pathways by modifying catalyst structure and reaction conditions.
A new
annulation strategy for the synthesis of trans-bicyclic
sulfamides is described. The Pd-catalyzed alkene carboamination
reactions of 2-allyl and cis-2,5-diallyl pyrrolidinyl
sulfamides with aryl and alkenyl triflates afford the fused bicyclic
compounds in good yields and with good diastereoselectivity (up to
13:1 dr). Importantly, by employing reaction conditions that favor
an anti-aminopalladation mechanism, the relative
stereochemistry between the C3 and C4a stereocenters of the products
is reversed relative to related Pd-catalyzed carboamination reactions
that proceed via syn-aminopalladation.
Pathways. -Optimized conditions concerning the substrates, the catalyst and the reaction medium favor the desired anti-aminopalladation mechanism to produce the ring systems with a reversed relative stereochemistry at C-3/C-4. Various 5,6-bicyclic structures and a 6,6-bicyclic one are prepared, which represent intermediates in polycyclic alkaloid synthesis. In the case of triflate (VI), a complex mixture is obtained and determination of the diastereoselectivity is only possible after hydrogenation. The transformation of diallyl substrate (VIII) requires a reduced time in order to avoid isomerization of the remaining olefin residue. -(BABIJ, N. R.; MCKENNA, G. M.; FORNWALD, R. M.; WOLFE*, J. P.; Org. Lett. 16 (2014) 12, 3412-3415, http://dx.
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