A New Synthesis of Sulfur‐, Nitrogen‐ and Oxygen‐Containing Eight‐Membered Ring Lactams

Abstract

Bi(NO3)3‐catalyzed ring expansion of five‐membered ring 1,4‐diketones in the presence of primary amines leads to eight‐membered ring lactams. When applied to starting materials with a tetrahydrothiophene or pyrrolidine moiety, tetrahydro‐2H‐1,4‐thiazocin‐3‐ones and hexahydro‐1,4‐diazocin‐2‐ones are obtained as representatives of these very rare heterocyclic systems. In the case of tetrahydrofuran derivatives, other reaction conditions are required and yields of tetrahydro‐2H‐1,4‐oxazocin‐3‐ones are very low.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Palladium‐Catalyzed Intramolecular Aryl Amination Reaction: An Expeditious Approach to the Synthesis of Chiral Benzodiazocine Derivatives

“…Most of these are either intermolecular or deal with achiral substrates. [7] We were encouraged to apply the palladium catalyzed aromatic carbon-nitrogen bond forming reaction involving the cross coupling of aryl halides (or triflates, nonaflates, mesitylates) and amines which has recently seen an upsurge in interest as a useful synthetic tool. [8] Amination of aryl bromides under tin free conditions, initially achieved both by Buchwald [9a] and Hartwig [9b] groups, mainly focused on the intermolecular amination of aryl bromides or iodides to give substituted anilines.…”

Synthesis of Benzo[c]azocanones and Indeno[1,2‐b]pyrroles from Oxoindanecarboxylates

“…To elucidate the scope of this re-action regarding the amine, we attempted to convert BnNH 2 , EtOCH 2 CH 2 NH 2 , iPrNH 2 , CyNH 2 , GlyOtBu, and β-AlaOtBu, [19] but only in the case of BnNH 2 was a product, 6c, obtained in low yield and low purity (Scheme 4, Table 1). Although we were convinced from our earlier work that the Bi-salt is required for the reaction, [11][12][13] when we attempted to convert ethyl ester 5b with MeNH 2 without Bi-additive, the product 6b was indeed formed. Again, several reaction parameters were screened, and it was found that conversion with two equivalents of amine at 100°C for 16 h gave optimal results, although the yield was still moderate (38 %).…”

“…The hitherto unknown oxoindanecarboxylates 5a and 5b, both containing a 1,4-diketone motif, were accessed starting from the corresponding β-oxo esters 4a [16] and 4b [17] and phenacyl bromide in good yields according to a standard protocol [13] previously used by us (Scheme 2).…”

“…[12] We have furthermore applied this reaction for the conversion of tetrahydrofuran, tetrahydrothiophene, and pyrrolidine derivatives to yield oxazocanes 2b, thiazocanes 2c, and diazocanes 2d. [13] From a mechanistic point of view, the ring-enlargement seems to proceed via an azabicyclo [3.3.0]octane intermediate 3, which was proved in one case by isolation and crystallographic characterization of an example with R = H and X = CH 2 as the imine-tautomer. [14] A similar C1-C5 bond cleavage reaction with the formation of benzo[c]azocanes was actually reported before with tricyclic oxaziridines.…”

Dihydropyridazine Derivatives with Cyclopenta‐, Benzo‐, Furo‐, Thiopyrano‐ and Pyrido‐Annulation

“…The interconversion of the five-membered ring in starting materials 1 to an eight-membered ring in products 2 is assumed to proceed through intermediate 3 with a bicyclo [3.3.0] skeleton. [2] Furthermore, we have been able to convert tetrahydrothiophenes 1 (X = S) and pyrrolidines (X = N-PG) to respective thiazocinones 4 (X = S) [3] and diazocinones (X = N-R D ), [4] the latter having a fourth point of diversity R D , which was introduced after deprotection of secondary amine N-PG. [2] Furthermore, we have been able to convert tetrahydrothiophenes 1 (X = S) and pyrrolidines (X = N-PG) to respective thiazocinones 4 (X = S) [3] and diazocinones (X = N-R D ), [4] the latter having a fourth point of diversity R D , which was introduced after deprotection of secondary amine N-PG.…”