Disila‐Okoumal: A Silicon Analogue of the Ambergris Odorant Okoumal

Abstract

Two-fold sila-substitution (C/Si exchange) in the saturated ring of the tetrahydronaphthalene skeleton of the ambery odorant okoumal (5) provides disila-okoumal (6). The okoumal isomers 5 a-d were synthesized from 1-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-2-naphthyl)ethanone (7), and the silicon analogues 6 a-d were synthesized from 1-(5,5,8,8-tetramethyl-5,8-disila-5,6,7,8-tetrahydro-2-naphthyl)ethanone (8). Detailed olfactory properties of 5 a-d and 6 a-d are reported, together with the respective threshold values. All enantiomers of okoumal and disila-okoumal exhibit typical ambery odor notes with woody facets, as is characteristic of okoumal and karanal, but a stereocenter at the 2-position was found to be of utmost importance for the odor thresholds; the lowest value of 0.31 ng per L air was measured for the 2R-configured silicon compounds 6 a and 6 c.

Synthesis and Olfactory Properties of a 6′‐Silasubstituted “Spiro[4.5]‐δ‐Damascone”

“…Phenylphosphonic acid (300 mg, 1.90 mmol) was added and the reactor was sealed. Elemental analysis calcd (%) for C 6 2-(1'-Allylsilolan-1'-yl)-3-methylpent-4-enenitrile (13) At À40 8C, a3 m solution of BuLi in hexane (112 mL, 336 mmol) was added in small portions to as tirred solution of diisopropylamine (18.1 g, 179 mmol) in THF (240 mL). The autoclave was then allowed to cool to RT,a nd the reaction mixture concentrated in vacuo to afford crude 3-methylpent-4-enal (17).…”

“…The authors would like to acknowledge and cordially thank Dr. ThierryG ranier,a sw ell as his co-inventorsN icolas Anorga, Dr. Markus Gautschi and Dr.B ernadette Bourdin Trunz for the discovery of the Spiro[4.5]-d-damascone lead (6). [4] In the course of our joint collaboration, we are grateful to Prof. Dr.R einhold Ta cke and Dr.S teffen Dçrrich for experiments on the doublemetathesis route via intermediate 8.…”

“…[5] Generally, more substantive odorants result from such sila-substitutions, and in some cases, such as ford isila-Okoumal [6] and silicon-based patchouli odorants, [7] the odor thresholds improved as well and compensated for the loss in volatility.Int he case of Spirogalbanone (5), however,t he odor detection threshold (th) increased by af actor of about 170 from 0.023 ng L À1 air to 3.8 ng L À1 for the more potent a-isomer. [5] Generally, more substantive odorants result from such sila-substitutions, and in some cases, such as ford isila-Okoumal [6] and silicon-based patchouli odorants, [7] the odor thresholds improved as well and compensated for the loss in volatility.Int he case of Spirogalbanone (5), however,t he odor detection threshold (th) increased by af actor of about 170 from 0.023 ng L À1 air to 3.8 ng L À1 for the more potent a-isomer.…”

Odorant Design Based on the Carbon/Silicon Switch Strategy

“…4), and the olfactory properties (including the odor thresholds) of the C/Si analogues 21a/21b, 22a/22b, 23a/23b, and 24a/24b were evaluated ( Table 8) [31].…”

Carbon/Silicon Exchange at the Apex of Diphos‐ and Triphos‐Derived Ligands – More Than Just a Substitute?

“…Even second‐sphere effects are of importance when designing metal complexes for catalytic applications While a detailed understanding of alterations in activity as a result of changing donor atoms on a metal center is provided in the literature and chemists are conscious of second‐sphere effects, there is no awareness that such changes can also be introduced by a stepwise replacement of C by Si in the ligand periphery. C/Si exchange, however, has been reported to have a significant influence on the chemical and physical properties of explosives and odorants as well as the biological properties of drugs . Furthermore, contrary to their carbon derivatives, numerous siloles are known to reveal strong light emission and absorption in the longer‐wavelength region .…”