研究目的
To study the correlation of macrocycle nonplanarity and catalytic activity of free base porphyrins in detail.
研究成果
The study demonstrates that increasing saddle-type distortion in porphyrins enhances their organocatalytic activity in sulfa-Michael reactions, attributed to better accessibility of the inner core N/N–H groups. Both steric and electronic factors are essential for designing effective porphyrin organocatalysts, with conformational engineering playing a key role. Future work should focus on combining electronic and conformational modulation for improved catalysts.
研究不足
The DFT calculations did not fully support the observed trends in catalytic activity, as changes in partial charges were small and may be outweighed by steric factors. Differentiating the influence of steric and electronic factors is nontrivial, and finding porphyrins with the same conformation but different electronic structures or vice versa remains difficult.
1：Experimental Design and Method Selection:
The study involved synthesizing a series of six β-substituted porphyrins ('H2EtxTPPs' 1–6) and using them as organocatalysts in sulfa-Michael reactions to correlate nonplanarity with catalytic activity. DFT calculations with B3LYP functional and 6-31G(d,p) basis set were employed to analyze electronic properties.
2：Sample Selection and Data Sources:
Porphyrins 1–6 were synthesized according to literature methods. Crystal structure coordinates were taken from the Cambridge Crystallographic Data Centre (CCDC) for DFT calculations.
3：List of Experimental Equipment and Materials:
Microliter syringes, analytical balance, 1 mL screw-cap vials, 5 mL round-bottom flasks, solvents (CH2Cl2, degassed and dried over Al2O3), nucleophile (tert-butyl benzylmercaptan, 7), Michael acceptor (phenyl vinyl sulfone, 8), internal standard (CH2Br2), and catalysts (porphyrins 1–6).
4：6).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Reactions were carried out under argon atmosphere. Catalysts, nucleophile, and Michael acceptor were dissolved in CH2Cl2, stirred at RT for 24 h in the dark. Internal standard was added, and conversion was determined via quantitative 1H NMR spectroscopy.
5：Data Analysis Methods:
Conversion was calculated by comparing product integrals with internal standard integrals in 1H NMR spectra. DFT calculations used Gaussian 09 software with PCM for solvent effects, and Mulliken charge analysis was performed.
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