**4. Conclusions**

Ten novel quaternary ammonium salt bifunctional phase-transfer organocatalysts based on a chiral (+)-camphor framework were prepared. Starting from camphor-derived 1,3-diamines, catalysts **I**–**X** were synthesized in a four-step sequence: Boc protection– benzylation–Boc deprotection–reaction with iso(thio)cyanate/squaramate. The catalysts prepared bear either a (thio)urea or squaramide hydrogen bond donor and possess either a trifluoroacetate or iodide counteranion. The quaternary iodide ammonium salts **II**, **V**, and **VIII** were formed from the corresponding trifluoroacetates **I**, **IV**, and **VII**, respectively, via anion methathesis with an excess of NaI. The phase-transfer catalysts have been fully characterized; the stereochemistry at the C-2 chiral center was unambiguously determined. Their organocatalytic activity was investigated in the electrophilic functionalization of the β-keto ester **9**. The α-fluorination and chlorination of β-keto ester **9** proceeded to full conversion, affording the desired products **10** and **11** with low enantioselectivity (up to 29% ee). α-Hydroxylation and ring opening of *N*-tosylaziridine **14** gave no product. Finally, the Michael addition of glycine Schiff base **16** to methyl acrylate (**17**) gave the expected product **18** with full conversion and up to 11% ee.

**Supplementary Materials:** The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/molecules28031515/s1. Synthesis and characterization data; HPLC data; copies of 1H- and 13C-NMR spectra; copies of HRMS reports; structure determination by X-ray diffraction analysis. Figure S1. Applied organocatalysts **I**–**IX**. Figure S2. Molecular structure of compound **VI-Br**. Thermal ellipsoids are shown at 50% probability. Figure S3. Molecular structure of compound **III**. Thermal ellipsoids are shown at 50% probability. Table S1. Evaluation of organocatalysts **I**–**IX** in the fluorination of β-keto ester **9**. Table S2. Further evaluation of organocatalysts **III**, **VIII**, and **IX** in the fluorination of β-keto ester **9**. Table S3. Evaluation of organocatalysts **II**, **III**, **VI**–**VIII**, and **IX** in the chlorination of β-keto ester **9**. Table S4. Evaluation of organocatalysts **III**, **IV**, **VII**, **VIII**, and **IX** in the hydroxylation of β-keto ester **9**. Table S5. Evaluation of organocatalysts **IV**, **VIII**, and **IX** in the addition of β-keto ester **9** to tosylaziridine **14**. Table S6. Evaluation of organocatalysts **I**, **III**–**V**, **VII**, **VIII**, and **IX** in the addition of *tert*-butyl 2-((diphenylmethylene)amino)acetate (**16**) to methyl acrylate (**17**). Table S7. Correlation between the multiplicity of the H–C(3)-*endo* proton (He) and the *endo* absolute configuration at the C-2 chiral center of compounds **1a**, **3b**, **5a**, **7a**,**b**, and **III**–**X**. Table S8. Crystal data and structure refinement for compound **VI-Br**. Table S9. Crystal data and structure refinement for compound **III**.

**Author Contributions:** Conceptualization, L.C., U.G. and J.S.; methodology, L.C. and U.G.; software, L.C., U.G. and J.S.; validation, L.C., U.G., J.S. and M.W.; formal analysis, L.C., H.B. and M.W.; investigation, L.C., M.W. and U.G.; resources, L.C., U.G., M.W. and J.S.; data curation, L.C., U.G., J.S., H.B., M.W. and B.Š.; writing—original draft preparation, L.C. and U.G.; writing—review and editing, L.C., U.G., J.S., M.W., F.P. and B.Š.; visualization, L.C., U.G. and J.S.; supervision, U.G. and M.W.; project administration, U.G., M.W. and J.S.; funding acquisition, U.G. and J.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Slovenian Research Agency through grant P1-0179.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Sample Availability:** Samples of the compounds are available from the authors.
