Wavelength-dependent rearrangements of an α-dione chromophore: a chemical pearl in a bis(hypersilyl) oyster

Glotz, Gabriel; Drusgala, Manfred; Hamm, Florian; Fischer, Roland C.; Došlić, Nađa; Kelterer, Anne-Marie; Gescheidt, Georg; Haas, Michael (2024) Wavelength-dependent rearrangements of an α-dione chromophore: a chemical pearl in a bis(hypersilyl) oyster. Chemical Science, 15 (12). pp. 4427-4433. ISSN 2041-6520

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Abstract

The symmetric bissilyl-dione 3 reveals two well-separated n → π* absorption bands at λmax = 637 nm (ε = 140 mol−1 dm3 cm−1) and 317 nm (ε = 2460 mol−1 dm3 cm−1). Whereas excitation of 3 at λ = 360/365 nm affords an isolable siloxyketene 4 in excellent yields, irradiation at λ = 590/630 nm leads to the stereo-selective and quantitative formation of the siloxyrane 5. These remarkable wavelength-dependent rearrangements are based on the electronic and steric properties provided by the hypersilyl groups. While the siloxyketene 4 is formed via a hitherto unknown 1,3-hypersilyl migration via the population of a second excited singlet state (S2, λmax = 317 nm, a rare case of anti-Kasha reactivity), the siloxyrane 5 emerges from the first excited triplet state (T1via S1λmax = 637 nm). These distinct reaction pathways can be traced back to specific energy differences between the S2, S1 and T1, an electronic consequence of the bissilyl substited α-dione (the “pearl”). The hypersilyl groups act as protective ‘‘oyster shell”, which are responsible for the clean formation of 4 and 5 basically omitting side products. We describe novel synthetic pathways to achieve hypersilyl substitution (3) and report an in-depth investigation of the photorearrangements of 3 using UV/vis, in situ IR, NMR spectroscopy and theoretical calculations.

Item Type:	Article
Uncontrolled Keywords:	wavelength-dependent rearrangements; hypersilyl; α-dione
Subjects:	NATURAL SCIENCES > Chemistry
Divisions:	Division of Physical Chemistry
Depositing User:	Ivana Vuglec
Date Deposited:	25 Mar 2026 09:51
URI:	http://fulir.irb.hr/id/eprint/11436
DOI:	10.1039/d4sc00064a

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