O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations.
Molecules. 2023 Mar 08; 28(6)M

Abstract

This paper presents the use of O,S-acetals in a new modification of the oxo-Friedel-Crafts-Bradsher cyclization. In this reaction, under mild reaction conditions (25 °C), three- and four-ring fused RO-acenes (major) and/or HO(CH₂)₂S-acenes (minor) are formed, the latter products having never been observed before in this type of cyclization. In this way, two electronically different fluorophores could be obtained in a single cyclization reaction, one of them having strong electron donor properties (+M effect of alkoxy groups) and the other having donor-acceptor properties (+M and -I effects of the HO(CH₂)₂S-group, Hammett's constants). Further increasing the reaction temperature, HCl concentration or prolonging reaction time, surprisingly, yielded a 2:1 mixture of cis and trans dimeric isomers, as the only products of this cyclization. The DFT calculations confirmed a greater stability of the cis isomer compared to the trans isomer. The formation of unexpected dimeric products and HO(CH₂)₂S-acenes sheds light on the mechanism of oxo-Friedel-Crafts-Bradsher cyclization, involving competitive O/S atom protonation in strained O,S-acetals and in strain-free side groups of intermediate species.

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Authors+Show Affiliations

Owsianik K

Division of Organic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łódź, Poland.

Różycka-Sokołowska E

Institute of Chemistry, Faculty of Science and Technology, Jan Długosz University in Częstochowa, Armii Krajowej 13/15, 42-201 Częstochowa, Poland.

Bałczewski P

Division of Organic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences, Sienkiewicza 112, 90-363 Łódź, Poland. Institute of Chemistry, Faculty of Science and Technology, Jan Długosz University in Częstochowa, Armii Krajowej 13/15, 42-201 Częstochowa, Poland.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

36985445

Citation

Owsianik, Krzysztof, et al. "O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations." Molecules (Basel, Switzerland), vol. 28, no. 6, 2023.

Owsianik K, Różycka-Sokołowska E, Bałczewski P. O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations. Molecules. 2023;28(6).

Owsianik, K., Różycka-Sokołowska, E., & Bałczewski, P. (2023). O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations. Molecules (Basel, Switzerland), 28(6). https://doi.org/10.3390/molecules28062474

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations. AU - Owsianik,Krzysztof, AU - Różycka-Sokołowska,Ewa, AU - Bałczewski,Piotr, Y1 - 2023/03/08/ PY - 2023/1/15/received PY - 2023/3/1/revised PY - 2023/3/6/accepted PY - 2023/3/30/medline PY - 2023/3/29/entrez PY - 2023/3/30/pubmed KW - Friedel–Crafts–Bradsher reactions KW - O,S-acetals KW - acenes KW - cyclization KW - electrophilic aromatic substitution KW - fluorescence JF - Molecules (Basel, Switzerland) JO - Molecules VL - 28 IS - 6 N2 - This paper presents the use of O,S-acetals in a new modification of the oxo-Friedel-Crafts-Bradsher cyclization. In this reaction, under mild reaction conditions (25 °C), three- and four-ring fused RO-acenes (major) and/or HO(CH2)2S-acenes (minor) are formed, the latter products having never been observed before in this type of cyclization. In this way, two electronically different fluorophores could be obtained in a single cyclization reaction, one of them having strong electron donor properties (+M effect of alkoxy groups) and the other having donor-acceptor properties (+M and -I effects of the HO(CH2)2S-group, Hammett's constants). Further increasing the reaction temperature, HCl concentration or prolonging reaction time, surprisingly, yielded a 2:1 mixture of cis and trans dimeric isomers, as the only products of this cyclization. The DFT calculations confirmed a greater stability of the cis isomer compared to the trans isomer. The formation of unexpected dimeric products and HO(CH2)2S-acenes sheds light on the mechanism of oxo-Friedel-Crafts-Bradsher cyclization, involving competitive O/S atom protonation in strained O,S-acetals and in strain-free side groups of intermediate species. SN - 1420-3049 UR - https://www.unboundmedicine.com/medline/citation/36985445/OS_Acetals_in_a_New_Modification_of_oxo_Friedel_Crafts_Bradsher_Cyclization_Synthesis_of_Fluorescent__Hetero_acenes_and_Mechanistic_Considerations_ DB - PRIME DP - Unbound Medicine ER -

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O,S-Acetals in a New Modification of oxo-Friedel-Crafts-Bradsher Cyclization-Synthesis of Fluorescent (Hetero)acenes and Mechanistic Considerations.Molecules. 2023 Mar 08; 28(6)M