| Literature DB >> 36103403 |
Oliver M Griffiths1, Steven V Ley1.
Abstract
N-heterospirocycles are interesting structural units found in both natural products and medicinal compounds but have relatively few reliable methods for their synthesis. Here, we enlist the photocatalytic generation of N-centered radicals to construct β-spirocyclic pyrrolidines from N-allylsulfonamides and alkenes. A variety of β-spirocyclic pyrrolidines have been constructed, including drug derivatives, in moderate to very good yields. Further derivatization of the products has also been demonstrated as has a viable scale-up procedure, making use of flow chemistry techniques.Entities:
Mesh:
Substances:
Year: 2022 PMID: 36103403 PMCID: PMC9552240 DOI: 10.1021/acs.joc.2c01684
Source DB: PubMed Journal: J Org Chem ISSN: 0022-3263 Impact factor: 4.198
Figure 1Strategies Developed to Access Spirocyclic Pyrrolidines.
Reaction Optimization
| entry | deviation from standard conditions | yield (%) |
|---|---|---|
| 1 | none | 80 (76) |
| 2 | no photocatalyst | 14 |
| 3 | no light | <5 |
| 4 | under air | 72 |
| 5 | MeCN solvent | 0 |
| 6 | DCE solvent | 62 |
| 7 | 0.1 M (step 2) | 80 |
| 8 | 0.025 M (step 2) | 78 |
| 9 | 2 equiv | 64 |
| 10 | 5 equiv | 82 |
| 11 | 5 min (step 1) | 76 |
| 12 | 4CzIPN used as PC | 72 |
Reaction conditions: 0.2 mmol, 1.0 equiv of N-allyltoluenesulfonamide, 1.5 equiv of 1,3-dichloro-5,5′-dimethylhydantoin, 3.0 equiv of methylenecyclohexane, 0.5 mol % (Ir[dF(CF3)ppy]2(dtbpy))PF6 (PC1), 4 mL total (step 2) of dichloromethane (DCM). 1H NMR conversion to the product.
Isolated yield.
Unreacted N–Cl intermediate observed as the major component by 1H NMR.
N-allyltoluenesulfonamide alone observed by 1H NMR.
N-Allylsulfonamide Scopea
Reaction conditions: 0.2 mmol, 1.0 equiv of N-allyltoluenesulfonamide, 1.5 equiv of 1,3-dichloro-5,5′-dimethylhydantoin, 3.0 equiv of methylenecyclohexane, 0.5 mol % (Ir[dF(CF3)ppy]2(dtbpy))PF6, 4 mL total (step 2) of DCM. a1.5 equiv of 1,3-dibromo-5,5′-dimethylhydantoin was used instead of 1,3-dichloro-5,5′-dimethylhydantoin.
1.5 equiv of 1,3-diiodo-5,5′-dimethylhydantoin was used instead of 1,3-dichloro-5,5′-dimethylhydantoin.
Starting material 1l was the sole observed product in the crude 1H NMR spectrum.
Exocyclic Olefin Scopea
Reaction conditions: 0.2 mmol, 1.0 equiv of N-allyltoluenesulfonamide, 1.5 equiv of 1,3-dihalo-5,5′-dimethylhydantoin, 3.0 equiv of olefin, 0.5 mol % (Ir[dF(CF3)ppy]2(dtbpy))PF6, 4 mL total (step 2) of DCM. aDiastereomeric ratios not able to be determined due to inseparability and substantial overlapping of peaks in the 1H NMR spectra of the isolated diastereomers.
2 equiv of olefin component used.
0.5 mol % 4CzIPN used as photocatalyst instead.
Halomethyl Derivatizations
Drug Derivativesa
Reaction conditions: 0.2 mmol, 1.0 equiv of N-allyltoluenesulfonamide, 1.5 equiv of 1,3-dihalo-5,5′-dimethylhydantoin, 3.0 equiv of olefin, 0.5 mol % Ir[dF(CF3)ppy]2(dtbpy)PF6, 4 mL total (step 2) of DCM. a1,3-diiodo-5,5′-dimethylhydantoin used and the resulting alkyl iodide subjected to hydrodehalogenation conditions with 4.0 equiv TTMSS in situ as in Table a.
Scheme 1Multigram Continuous Flow Construction of β-Spirocyclic Pyrrolidine 3ad