Attempts to Synthesize a Thiirane, Selenirane, and Thiirene by Dealkylation of Chalcogeniranium and Thiirenium Salts

Thiiranium salts [Ad(2)SR]X-+(-)(5,8,9,11,12; X-=Tf2N-(Tf=CF3SO2), SbCl6-) and seleniranium salts [Ad(2)SeR]X-+(-)(14,16,17,23-25; X-=Tf2N-, BF4-, CHB11Cl11-, SbCl6-) are synthesized from strained alkene bis(adamantylidene) (1). The disulfides and the diselenides (Me3SiCH2CH2E)(2)(4,13), (tBuMe(2)SiCH(2)CH(2)E)(2)(7,22), and (NCCH2CH2E)(2)(10,15; E=S, Se) have been used. The thiirenium salts [tBu(2)C(2)SR]X-+(-)(34) and [Ad(2)C(2)SR]X-+(-)(35,36) are prepared from the bis-tert-butylacetylene (2) and bis-adamantyl-acetylene (3) with R=Me(3)SiCH(2)CH(2)andtBuMe(2)SiCH(2)CH(2). Attempts to cleave off the groups Me3SiCH2CH2,tBuMe(2)SiCH(2)CH(2), and NCCH(2)CH(2)resulted in thiiranes27,30. No selenirane Ad(2)Se (33) is formed from seleniranium salts, instead cleavage to the alkene (1) and diselenide (13,15) occurs. The thiirenium salt [Ad(2)C(2)SCH(2)CH(2)SiMe(3)]+Tf2N-(35) does not yield the thiirene Ad(2)C(2)S (37), the three-membered ring is cleaved, forming the alkyne (3) and disulfide (4). All compounds are characterized by ESI mass spectra, NMR spectra, and by quantum chemical calculations. Crystal structures of the salts8,12,25,17,26,36and the thiiranes27,30are presented

Epimerization of trans-Cycloalkenes with the X–C=C–SeR*-Unit – The Steric Demand of X = H, F, Cl, Br, I, Me, Et and CF3

Trans-cycloalkenes with the X–C=C–SeR*-unit and ring sizes from 9 to 20 have been synthesized. Bond the selenium atom is the chiral (S)-o-(1-Methoxypropyl)phenyl-residue R*, and X = H, F, Cl, Br, I, Me, Et and CF3. The planar-chiral trans-cycloalkenes in combination with the chiral residue R* exist as two diastereomers. These can be distinguished in principle by NMR spectroscopy. We have studied the epimerization of the trans-cycloalkenes, i.e., the 180° rotation of the X–C=C-unit through the cavity of the ring. The measurements were done with variable temperature 13C NMR spectroscopy in the range from –110 to 140°C. The obtained values of the Gibbs energy of activation ΔG‡C depend strongly on the ring size. Furthermore, the ΔG‡C values show dramatic steric effects due to the groups X. The steric requirement of X increases in the series H << F << Cl < Me < Br < I < Et < CF3. Here, F is significantly larger than H, and CF3 is larger than Et. The corresponding iPr-compounds could not be synthesized. The transition state structures of the ring inversion for ring sizes 8–20 were calculated at the DFT level of theory

Identification of the Sex Pheromone of a Protected Species, the Spanish Moon Moth Graellsia isabellae

Sex attractant pheromones are highly sensitive and selective tools for detecting and monitoring populations of insects, yet there has been only one reported case of pheromones being used to monitor protected species. Here, we report the identification and synthesis of the sex pheromone of a protected European moth species, Graellsia isabellae (Lepidoptera: Saturniidae), as the single component, (4E,6E,11Z)-hexadecatrienal. In preliminary field trials, lures loaded with this compound attracted male moths from populations of this species at a number of widely separated field sites in France, Switzerland, and Spain, clearly demonstrating the utility of pheromones in sampling potentially endangered insect species