title: Synthesis and Olfactory Properties of a 6'-Silasubstituted "Spiro[4.5]-δ-Damascone".
abstract: The silicon analogue of the potent spirocyclic δ-damascone odorant 6 was synthesized from allyltrichlorosilane (15) and but-2-en-1-ol (16). The latter was transformed to 3-methylpen-4-enenitrile (11) by Saucy-Marbet reaction with ethoxyethane and subsequent treatment with HONH2⋅HCl. The resulting γ,δ-unsaturated nitrile 11 was silylated with 1-allyl-1-chlorosilolane (14), which was prepared from allyltrichlorosilane (15) and the bis-Grignard reagent of 1,4-dichlorobutane. Metathetic ring closure employing the Grubbs I catalyst, followed by DIBAL reduction with non-aqueous work up, Grignard reaction with prop-1-en-1-ylmagnesium bromide, and Attenburrow MnO2oxidation concluded the synthesis. The target compound was found to be olfactorily related to the spiro[4.5]-δ-damascone lead, but approximately 900 times weaker. In a type of enol Brook rearrangement, it thermally decomposes however to 3,6-dihydro-2H-1,2-oxasilocine (20), which surprisingly is a damascone odorant as well; although, 12 000 times weaker.
authors.affiliation: Fragrance Research, Givaudan Schweiz AG, Überlandstrasse 138, 8600, Dübendorf, Switzerland.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Lovchik
authors.affiliation: Fragrance Research, Givaudan Schweiz AG, Überlandstrasse 138, 8600, Dübendorf, Switzerland.
authors.forename: Philip
authors.identifier: http://orcid.org/0000-0002-4801-5389
authors.initials: P
authors.lastname: Kraft
keywords: Brook rearrangement; fragrances; metathesis; rose ketones; silicon; spiro compounds