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Chem Biodivers

Title:		"Synthesis by ring-closing alkyne metathesis with selective hydrogenation, and olfactory comparison of (7E)- and (7Z)-cyclohexadec-7-enone (Aurelione((R)) )"
Author(s):		Mathys M; Kraft P;
Address:		"Givaudan Schweiz AG, Fragrance Research, Uberlandstrasse 138, CH-8600 Dubendorf, (phone: +41-44-8242520; fax: +41-44-8242926)"
Journal Title:		Chem Biodivers
Year:		2014
Volume:		11
Issue:		10
Page Number:		1597 - 1607
DOI:		10.1002/cbdv.201400011
ISSN/ISBN:		1612-1880 (Electronic) 1612-1872 (Linking)
Abstract:		"Both C=C-bond isomers of cyclohexadec-7-enone (6, Aurelione((R)) ) were selectively synthesized via cyclohexadec-7-ynol (16) by ring-closing alkyne metathesis of icosa-2,18-diyn-9-ol (15), employing an in situ-formed catalyst from Mo(CO)6 and 4-(trifluoromethyl)phenol. Pyridinium chlorochromate (PCC) oxidation and subsequent Lindlar hydrogenation afforded the (7Z)-configured isomer (7Z)-6, while hydrosilylation of the intermediate cyclohexadec-7-ynone (17), followed by desilylation, provided the (7E)-configured cyclohexadec-7-enone ((7E)-6). The substrate for the alkyne metathesis was prepared from cycloheptanone (7) by cycloaddition of chloromethylcarbene to its trimethylsilyl enol ether 8, and subsequent ring enlargement of the adduct 9 under rearrangement to 2-methylcyclooct-2-enone (10), which was subjected to Weitz-Scheffer epoxidation and Eschenmoser-Ohloff fragmentation to non-7-ynal (12). Its reaction with the Grignard reagent of 11-bromoundec-2-yne (14), prepared from the corresponding alcohol 13 by Appel-Lee bromination, furnished the icosa-2,18-diyn-9-ol (15). While both isomers of cyclohexadec-7-enone (6) possess warm and powdery musk odors with tobacco-type ambery accents, (7Z)-6 is more animalic and waxy, whereas (7E)-6 was found to be more floral, sweet, and hay-like in tonality. Interestingly, however, with odor detection thresholds of 2.0 ng/l air and 2.3 ng/l air, respectively, both (7Z)-6 and (7E)-6 were found to be almost identical in their odor strength, with the (7Z)-6 being only very slightly more powerful"
Keywords:		"Alkynes/*chemical synthesis/*chemistry Catalysis Cyclization Hydrogenation Ketones/*chemical synthesis/*chemistry Macrocyclic Compounds/*chemical synthesis/*chemistry Models, Molecular Molecular Conformation Molecular Structure Odorants/*analysis Stereois;"
Notes:		"MedlineMathys, Marion Kraft, Philip eng Switzerland 2014/10/21 Chem Biodivers. 2014 Oct; 11(10):1597-607. doi: 10.1002/cbdv.201400011"