biostudies-literatureHung CEMinistry of Education (MOE), TaiwanNational Science and Technology Council, TaiwanNational Science and Technology CouncilJapan Science and Technology AgencyJapan Society for the Promotion of Sciencee02053https://www.ebi.ac.uk/biostudies/studies/S-EPMC12462229biostudies-literatureUnknown31(54)We present herein a systematic study on the cyclodimerization of (trialkylsilyl)ethynyl-substituted derivatives of indeno[2.1-b]fluorene and fluoreno[2,3-b]fluorene, which incorporate an open-shell meta-quinodimethane (m-QDM) unit. Our investigation focuses on the influence of different alkyl groups (methyl, isopropyl, or cyclohexyl) attached to the silyl moiety. Upon generation from the precursor diols via treatment with SnCl₂, these m-QDM derivatives yielded cyclodimers with an anti-configuration. The reaction yields varied significantly, ranging from virtually zero to quantitative, depending on the steric bulk of the alkyl group. Furthermore, the regioselectivity of bond formation (Head versus Tail) with respect to the ethynyl-allenyl radical resonance forms was also notably Chemistry (Weinheim an der Bergstrasse, Germany)Taming m-Quionodimethanes by Dispersion Force: Cyclodimerization of (Trialkylsilyl)Ethynyl-Substituted Indeno[2,1-b]Fluorenes and Fluoreno[2,3-b]Fluorenes.PMC12462229113–2113‐M‐A49‐009JP24K01468113-2113-M-A49-009JPMJCR20R1MOE-113-YSFMS-0010-001-P1Lin HCRout YCheng YJTobe YIe YMiyoshi HHung CEOzawa RHisaki IfalseTaming m-Quionodimethanes by Dispersion Force: Cyclodimerization of (Trialkylsilyl)Ethynyl-Substituted Indeno[2,1-b]Fluorenes and Fluoreno[2,3-b]Fluorenes.We present herein a systematic study on the cyclodimerization of (trialkylsilyl)ethynyl-substituted derivatives of indeno[2.1-b]fluorene and fluoreno[2,3-b]fluorene, which incorporate an open-shell meta-quinodimethane (m-QDM) unit. Our investigation focuses on the influence of different alkyl groups (methyl, isopropyl, or cyclohexyl) attached to the silyl moiety. Upon generation from the precursor diols via treatment with SnCl₂, these m-QDM derivatives yielded cyclodimers with an anti-configuration. The reaction yields varied significantly, ranging from virtually zero to quantitative, depending on the steric bulk of the alkyl group. Furthermore, the regioselectivity of bond formation (Head versus Tail) with respect to the ethynyl-allenyl radical resonance forms was also notably 2025-01-01T00:00:00Z2025 Sep2026-06-03T20:13:31.394Z2026-05-01T03:11:03.805ZS-EPMC124622294082753910.1002/chem.202502053