Reaction of trifluoromethanesulfonamide with alkenes and cycloocta-1,5-diene under oxidative conditions. Direct assembly of 9-heterobicyclo[4.2.1]nonanes

Abstract

Reactions of trifluoromethanesulfonamide with α-methylstyrene, 2-methylpent-1-ene, and cycloocta-1,5-diene in the system t-BuOCl-NaI were studied. In the reaction with α-methylstyrene 1-iodo-2-phenylpropan-2-ol was the only isolated product. The reaction with 2-methylpent-1-ene gave a mixture of N,N′-(2-methylpentane-1,2-diyl)bis(trifluoromethanesulfonamide), trifluoro-N-(2-hydroxy-2-methylpentyl)-methanesulfonamide, and N, N′-[oxybis(2-methylpentan-2,1-diyl)]bis(trifluoromethanesulfonamide). Trifluoromethanesulfonamide reacted with cycloocta-1,5-diene to produce a mixture of 2,5-diiodo-9-(trifluoromethylsulfonyl)-9-azabicyclo[4.2.1]nonane and 2,5-diiodo-9-oxabicyclo[4.2.1]nonane; this reaction may be regarded as the first example of direct assembly of bicyclononane skeleton.We recently showed that aziridination of styrene with trifluoromethanesulfonamide in the oxidative system t-BuOCl-NaI · 2 H 2 O leads to formation of both linear structures I and II and heterocyclization product, 2,5-diphenyl-1,4-bis(trifluoromethylsulfonyl)piperazine (III) [1]. The structure of III was proved by X-ray analysis, and a mechanism involving intermediate formation of 2-phenyl-1-trifluoromethylaziridine was proposed [1]. However, the formation of substituted piperazine instead of expected aziridine contradicted the data reported by Minakata et al. [2], according to which aziridines were obtained in reactions of styrene and other alkenes with sulfonamides under analogous conditions due to strong electron-withdrawing effect of the CF 3 group [1]. We tried to reproduce the conditions described in [2] more accurately and carried out the reaction of styrene with trifluoromethanesulfonamide in the presence of anhydrous sodium iodide. In this case, we isolated compounds I and II and 2,6-diphenyl-1,4-bis(trifluoromethylsulfonyl)piperazine (IV) which is isomeric to III [3].In the present work we studied reactions of trifluoromethanesulfonamide with α-methylstyrene, 2-methylpent-1-ene, and cycloocta-1,5-diene under oxidative conditions (in the presence of t-BuOCl-NaI or t-BuOCl-NaI · 2 H 2 O) and analyzed possible ways of formation of the corresponding products.Taking into account that α-methylstyrene reacted with trifluoromethanesulfonamide in a way similar to styrene [2], i.e., with formation of the corresponding aziridine, and that the reaction direction strongly depends on the composition of the oxidative system, α-methylstyrene (V) was brought into reaction with trifluoromethanesulfonamide in two systems containing NaI · 2H 2 O or anhydrous NaI (as in [2]). In both cases, the only product was 1-iodo-2-phenylpropan-2-ol (VI) (Scheme 1). Compound VI is likely to be formed via iodination of α-methylstyrene with t-BuOI to

Iodotriflamdation vs. Electrophilic Aromatic Iodination in the Reaction of N‐Phenyltriflamide with Alkenes

“…Product 11 was verified by NMR spectroscopy and elemental analysis. Compounds 13 and 14 are identical to the earlier obtained ones by the reaction of triflamide with vinylcyclohexane and α ‐methylstyrene, respectively.…”

“…Finally, with α‐methylstyrene 5 , only compound 6 and iodoalcohol 14 were formed. As in the earlier studied reaction of α ‐methylstyrene with triflamide, no product of iodotriflamidation of the alkene was formed, apparently, due to steric hindrances created by the α ‐methyl group in 5 .…”

“…These results clearly demonstrated that the reactivity of triflamide is principally different from that of arenesulfonamides, which under the same conditions give aziridines . Vinylcyclohexane reacted in a similar way, while with p ‐chlorostyrene no piperazine derivatives were formed and α‐methylstyrene in the same system gave only iodoalcohol, 1‐iodo‐2‐phenylpropan‐2‐ol …”

Unsaturated Derivatives of Trifluoromethanesulfonamide

“…Similarly to the oxidative triflamidation of linear dienes shown in Scheme , the oxidative reaction between cycloocta‐1,5‐diene and triflamide does not give any unsaturated products, but affords the two bicyclic products 111 and 112 , representing the first examples of one‐step assembling of bicyclononane backbones (Scheme ) . The structures of both products were established by X‐ray analysis.…”

1,4-Diphenyl-1,3-butadiene and 1,1,4,4-Tetraphenyl-1,3-butadiene in the Reactions of Oxidative Sulfamidation and Trifluoroacetamidation

“…The reactions of oxidative triflamidation of dienes in the oxidative system ( t ‐BuOCl+NaI) proceed in different manner, leading to the products of 1,2‐ or 1,4‐addition with heterocyclization . With 1,4‐ or 2,3‐dimethylated butadienes‐1,3, the properly methylated 3,6‐bis(triflyl)diazabicyclo[3.1.0]hexanes were formed via two successive heterocyclizations …”