Ammonium formate-based one-pot reductive Heck reactions for the construction of cyclic sulfonamides

Chemistry of Bridged Lactams: Recent Developments

“…In 2017, Evans and co-workers in the continuation of their studies on bridged sultams reported an improved method for the synthesis of saturated sultams via intramolecular reductive Heck reaction (Figure 16) [40]. The use of a single Pd catalyst and a broad substrate scope are noteworthy features of this method.…”

Reduction of Substituted Benzo-Fused Cyclic Sulfonamides with Mg-MeOH: An Experimental and Computational Study

“…To this end, we initially revisited our previously studied benzo-fused cyclic sulfonamides 7a and 7b , which can be conveniently accessed via an intramolecular Heck process. 11 , 12 As shown in Scheme 2 , marked differences in reactivity were observed with Mg-MeOH based upon the presence and relative position of the methoxy substituents.…”

The Titanium-Mediated Double Reductive Cleavage of Cyclic Sulfonamides for the Synthesis of Aryl Pyrrolidines

“…However, several years ago our group speculated that, if a cyclic sulfonamide of the type 1 was employed, a double reductive excision of the sulfonyl group might produce an aryl amine of the type 2 (see Scheme ). Compounds of type 1 can be formed from RCM derived dihydropyrroles 3 , via a reductive intramolecular Heck reaction sequence . Furthermore, where applicable (R′ ≠ H), we have shown that this carbon–carbon bond-forming process favors generation of the more sterically encumbered quaternary product. , Overall, we felt that the sequence 3 → 2 , featuring a traceless N-protecting group which facilitates the formation of an sp 2 –sp 3 carbon–carbon bond (that may be quaternary), constitutes an efficient and attractive means for the construction of aryl amines ( 2 ).…”

“…In light of the success with the low-valent titanium method, a range of alternative examples bearing different aromatic (R and R′) and benzylic (R′′) substituents were considered (Table ). Substrates 8b – 8o were prepared according to our previously reported Heck hydrogenation sequence, and applying the conditions outlined in Table above their behavior in the presence of low-valent titanium was evaluated. As shown in Table , entry 1, the unsubstituted cyclic amide 8b smoothly gave 9b in a yield comparable to the Li-NH 3 method .…”

“…Again, in this case, the use of more equivalents of Ti­(IV) was not studied. In the final set of examples, we incorporated a substituent into the R′′ position taking advantage of the high degree of regioselectivity , that can be obtained for intramolecular Heck reactions of trisubstituted dihydropyrroles of the type 3 (Scheme ). As entries 8–13 indicate, in all cases reasonable to good yields of the resultant pyrrolidine compounds, 9j – 9o were obtained.…”