Rh(II)/Mg(O^tBu)₂-Catalyzed Tandem One-Pot Synthesis of 1,4-Oxazepines and 1,4-Oxazines from N-Sulfonyl-1,2,3-triazoles and Glycidols

Abstract

A novel, one-pot route for the synthesis of nonaromatic ring-fused 1,4-oxazepines and 1,4-oxazines has been developed. The reaction features a sequential rhodium(II)-catalyzed reaction of N-sulfonyl-1,2,3-triazoles with glycidols, followed by a regioselective Lewis acid Mg(OBu)-catalyzed intramolecular ring-opening reaction. It has been found that the regioselectivity in the epoxide ring-opening was largely determined by the substituents on the glycidols. Thus, substituted glycidols (R ≠ H) afforded seven-membered oxazepine derivatives selectively, while unsubstituted glycidols (R = H) afforded six-membered oxazine derivatives. Plausible reaction pathways are elucidated and supported by experiments with several glycidols bearing different substituents around the epoxide functionality.

Synthesis and Characterization of Tetrachloro-1,3-Oxazepine Derivatives and Evaluation of their Biological Activities

“…Oxazepines are heterocyclic unsaturated compounds, incorporating two hetero atoms (oxygen and nitrogen). There are many synthetic strategies for synthesis of oxazepines, using gold-, palladium-and rhodium-based catalysts, [1][2][3] under microwave irradiation, 4 and under catalyst-free conditions 5 as well; all these strategies leading to the formation of 1,3-oxazepines-4,7-diones. Oxazepines were synthesized to be evaluated for their potential activities, e.g.…”

“…antioxidant and anti-inflammatory activity, 6 as neuroleptic agents, 7 kinase inhibitors, 8 antimicrobial agents. 9 This paper describes 1,3-oxazepine-4,7-dione derivatives, synthesized by reactions of Schiff bases with TCPA, to provide information of synthetic method and the possible use of 6,7,8,9-tetrachloro [1,3]oxazepine-1,5-dione as an antibacterial (S. aureus, E. coli, Klebsiella spp.) and antifungal agent (Geotrichum spp.…”

Rhodium(II)‐Catalyzed Reaction of 1‐Tosyl‐1,2,3‐triazoles with Morita–Baylis–Hillman Adducts: Synthesis of 3,4‐Fused Pyrroles

“…Triazole chemistry has been extensively studied over the last decade, in which the N-sulfuryl-1,2,3-triazoles have been used as versatile synthetic precursors for the synthesis of nitrogencontaining heterocycles. [7][8][9][10][11] We have ag reat interesti na zaheterocycles ynthesis and N-sulfonyl-1,2,3-triazoles chemistry.W e have reported ap ractical and efficient method for divergent Scheme1.Rh II catalyzedreactionf or the construction of 3,4-fusedp yrroles.…”

“…Moreover, the use of 1,2-dichloroethane (DCE) or toluene as the solventd id not increase the yield of 3aa (entry [8][9]. The addition of Lewis acidh ave no positivee ffects (entry [10][11][12][13][14]. Finally, the reaction of MBH adduct 1a with 1.2 equiv of triazole 2a catalyzed by Rh 2 (Oct) 4 in CHCl 3 at 75 8Cw ere set as the optimum reaction conditions.…”

“…Gratifyingly,w ef ound that DBU promoted the cyclization smoothly to afford 4aa in 63 %y ield 1 [c] Rh 2 (OAc) 4 CHCl 3 -75 65 2 [c] Rh 2 (oct) 4 CHCl 3 -75 82 3 [c] Rh 2 (piv) 4 CHCl 3 -75 78 4 [c] Rh 2 (S-nttl) 4 CHCl 3 -75 67 5 [d] Rh 2 (oct) 4 CHCl 3 -75 86 6Rh 2 (oct) 4 CHCl 3 -75 90 [g] 7Rh 2 (oct) 4 CHCl 3 -85 88 8Rh 2 (oct) 4 CH 2 Cl 2 -75 77 9Rh 2 (oct) 4 toluene-75 73 (entry 7). Solvent effect was then tested with DBU as the base (entry [8][9][10][11]. The results show that the nonpolar solventt oluene is the best choice.M oreover, the yield did not increase either at ah igher reaction temperature or a lower reaction temperature (entry [12][13][14].W e envisioned that the additional oxidants would promote the reaction.…”