Rhodium(II)‐Catalyzed CH Insertions with {[(4‐Nitrophenyl)sulfonyl]imino}phenyl‐λ³‐iodane

Abstract

Dedicated to Prof. Dieter Seebach on the occasion of his 60th birthday (1 3.11.97) The [Rh,(OAc),]-catalyzed decomposition of {[(4-nitrophenyl)sulfonyl]imino}phenyl-13-iodane (NsN=IPh) resulted in formal insertions into CH bonds, activated by phenyl or vinyl groups, or by 0-substituents. Scope and limitations of the reaction were investigated. Yields of up to 84% were achieved in the most favorable cases. Yields were enhanced by electron-releasing substituents and decreased by steric hindrance. Aziridination competed with allylic insertion with olefinic substrates. The insertion reaction proceeded with retention of configuration. With chiral Rh" catalysts, a modest asymmetric induction was observed. A mechanism involving direct insertion by a Rh-complexed nitrene into the CH bond is proposed.

Rhodium(II)‐Catalyzed Oxidative Amination

“…Intermolecular amination experiments described by Müller using O 2 NC 6 H 4 SO 2 N=IPh (NsN=IPh) as the nitrene source underscore the value of certain rhodium(II) catalysts for C-H insertion (Scheme 17.5) [12,[34][35][36]. In accord with Breslow's finding, dirhodium carboxylates were demonstrated to catalyze the amination of allylic, benzylic, and adamantyl substrates.…”

Alkane Catalytic Functionalization by Carbene or Nitrene Insertion Reactions

“…In the rhodium case, some authors have proposed the concerted pathway, although not all the experimental evidences are in complete accord with this. For instance, work by Müller [103,126] proposed the one step mechanism on the basis of several experiments (also supported by Du Bois' studies) [127,128] whereas Dauban has shown some doubts due to the collection of contradictory data: [129] Hammett analyses supported the concerted pathway but KIE studies did not. DFT studies have shown that singlet and triplet states for Rh 2 -II, II -NR are very close in energy [130], and therefore small changes in the catalytic system could influence the reaction pathway.…”

“…The results shown in Table 6.5 regarding the use of adamantane are somewhat those expected, since the reaction site, a tertiary C-H bond, is more prone to undergo the insertion that the secondary C-H bonds of cyclohexane. Muller's work provided 76 % of the amine derivatives, as a mixture (71:5) of the products formed from the functionalization of tertiary and secondary sites, respectively (Table 6.5, entry 2) [103]. Catalytic systems described by Che (Ru, Mn) [112,113], and Nicholas [114] (Zn) were similar in activity, but at lower temperatures (Table 6.5, entries 3-6).…”

“…[103] The modest 31 % ee was later reproduced by Che with chiral Ru-and Mn-based porphyrin complexes and PhINTs (entry 2) [115], before Katsuki would describe with the same nitrene source the use of a Mn(Salen) catalyst for this transformation, with a 44 % ee (entry 1) [116]. A noticeable increase in enantioselection was introduced by Hashimoto, that rediscovered dirhodium complexes [117], with leucinate-derived ligands, reaching 70 % of ee (entry 4).…”

Gold versus Silver‐Catalyzed Intermolecular Hydroaminations of Alkenes and Dienes

“…Nevertheless, when MW heating was used, very poor results were obtained (Table 3, entry 41), again the silver-catalyzed reactions failed (Table 3, entries 40 and 42). For other terminal acyclic alkenes, such as oct-1-ene (1k), the HA took place in high yield only under solvent-free conditions using the gold complex as catalyst (Table 3, entries [43][44][45][46]. In this case, product 3ka was obtained together with regioisomeric sulfonamides at the 3-and 4-positions of the aliphatic skeleton, in 2/1.5/1 ratio.…”