“…(3) (100 mg, 0.209 mmol; Lutz et al, 2008) in pyridine (1.0 ml) was added acetic anhydride (0.5 ml), and the mixture was heated to reflux for 2 h. After cooling to room temperature the reaction mixture was diluted with deionized water (18 ml) to give a slurry which was extracted with ethyl acetate (3 Â 5 ml). The combined organic layers were successively washed with 1M aqueous HCl (2 Â 10 ml), deionized water (1 Â 10 ml) and brine (1 Â 10 ml), and dried over sodium sulfate.…”
The oxime derivative of [1.1.1]cyclophane cyclotriveratrylene (CTV) was ring expanded utilizing a Beckmann rearrangement to provide a ten-membered N-acetyl macrocyclic amide that crystallizes as a chloroform monosolvate in columnar assemblies manifesting an unusual disorder within the crystal. Columns made up of this structure consist of infinite columnar assemblies of alternating D and L enantiomers and therefore necessarily are made up of a racemate, yet the chiralities of individual molecules in adjacent columns are independent of one another, leading to the overall formation of a two-dimensional solid solution. The random arrangement of the columns within the structure leads to the emergence of a crystallographic mirror plane not reflected by the molecular symmetry, to a change of symmetry from Pna2(1) to Pnma and to whole-molecule disorder of the bowl-shaped molecules within the columns.
“…(3) (100 mg, 0.209 mmol; Lutz et al, 2008) in pyridine (1.0 ml) was added acetic anhydride (0.5 ml), and the mixture was heated to reflux for 2 h. After cooling to room temperature the reaction mixture was diluted with deionized water (18 ml) to give a slurry which was extracted with ethyl acetate (3 Â 5 ml). The combined organic layers were successively washed with 1M aqueous HCl (2 Â 10 ml), deionized water (1 Â 10 ml) and brine (1 Â 10 ml), and dried over sodium sulfate.…”
The oxime derivative of [1.1.1]cyclophane cyclotriveratrylene (CTV) was ring expanded utilizing a Beckmann rearrangement to provide a ten-membered N-acetyl macrocyclic amide that crystallizes as a chloroform monosolvate in columnar assemblies manifesting an unusual disorder within the crystal. Columns made up of this structure consist of infinite columnar assemblies of alternating D and L enantiomers and therefore necessarily are made up of a racemate, yet the chiralities of individual molecules in adjacent columns are independent of one another, leading to the overall formation of a two-dimensional solid solution. The random arrangement of the columns within the structure leads to the emergence of a crystallographic mirror plane not reflected by the molecular symmetry, to a change of symmetry from Pna2(1) to Pnma and to whole-molecule disorder of the bowl-shaped molecules within the columns.
“…3, Fig. 1) 17–19 , the substituent R 1 at the anti position to the hydroxyl group on the C=N moiety migrates to its nitrogen atom. Therefore, we envisioned that the configuration of the picropodophyllotoxin C4-oximes could also be confirmed by the corresponding C-ring expansion products via the Beckmann rearrangement.Figure 1Chemical structures of podophyllotoxin (1) and its derivatives (2, 2′, 3, 3′, and I-IV).
…”
As a continuation of our efforts to discover and develop natural-product-based insecticidal agents, three novel and unusual 7-membered lactam derivatives of podophyllotoxin were prepared by thionyl chloride-mediated ring-expanded Beckmann rearrangement. The steric configurations of 3a–c were unambiguously identified by X-ray crystallography. It demonstrated that the configuration of the picropodophyllotoxin C4-oximes could also be confirmed by the corresponding C-ring expansion products via Beckmann rearrangement. Moreover, it was obviously further testified that when picropodophyllones reacted with hydroxylamine hydrochloride, only E configuration of picropodophyllotoxin C4-oximes was selectively produced. Compounds 3b and 3c showed more potent pesticidal activity than toosendanin against oriental armyworm, Mythimna separata (Walker).
“…6 As part of our program to investigate apex-modified derivatives 7 of the bowl-shaped supramolecular scaffold cyclotriveratrylene (CTV), 8 we employed the Beckmann rearrangement to afford a ring expansion via the oxime 1 9 derived from CTV to afford the corresponding 10-membered CTV lactam 3, which depending upon the experimental conditions, was also accompanied by the product of an intramolecular electrophilic addition reaction affording an unexpected helical pentacycle 4 (Scheme 1). 10 We realized that this byproduct must have arisen from a cascade process wherein the intermediate nitrilium ion 2 formed in the Beckmann reaction was intercepted by one of the electron-rich veratrole rings of the macrocycle in a trans-annular process. We questioned whether this tandem 15 in the absence of a nucleophilic leaving group allowed time for the nitrilium ion to react with the -nucleophilic aromatic to give good to excellent yields of the TB-EAS products (Table 1).…”
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