The Synthesis of Cycloalkenes by the Intramolecular Wittig Reaction

Abstract

A simple synthesis of a series of bicyclo[m.n.0]‐1‐alkenes (m, n = 3,4,5) from 2‐oxocycloalkanecarboxylates by the intramolecular Wittig reaction is reported (see p. 70–72). The spectral properties (IR., 1H‐NMR. and 13C‐NMR.) of these annulated trisubstituted olefins are discussed.

Gold‐Mediated Isomerization of ­Cyclooctyne to Ring Fused Olefinic Bicycles

“…[54,55] The X-ray structure of 4[SbF 6 ] ( Figure 2) revealed that the gold center adopts an essentially linear coordination geometry with a C (carbene) -Au-(-C≡C-centroid ) angle of 176.7°. The Au-C(carbene) and Au-(-C≡C-centroid ) distances are 2.012 (4) 6 ], they were also synthesized via independent routes using authentic free alkenes bicyclo [3.3.0]oct-1(5)-ene (2) [56,57] and cis-bicyclo-[3.3.0]oct-2-ene (3) [58] (prepared following literature procedures), and (IPr)AuSbF 6 6 ] are rotated by about 79°(average) relative to the carbene Au(N-C-N) planes whereas in 6[SbF 6 ], this angle is about 74°. The structurally authenticated alkenes adducts of (IPr)Au + show a range of such inter-planar angles from essentially coplanar to nearly perpendicular suggesting that the relative alkene orientation is determined largely by steric factors, [37] presumably arising from interaction with methyl hydrogens on the IPr ligand.…”

“…[66] and was dried using 4 Å molecular sieves (see below as well). (IPr)AuCl, [54] (IPr)AuCl 3 , [67] [(SIPr)Au(cyclooctyne)][SbF 6 ], [25] and AgNTf 2 , [68] bicyclo [3.3.0]oct-1(5)-ene, [56,57,69] and cis-bicyclo [3.3.0]oct-2-ene [58] were prepared according to reported procedures. AgSbF 6 was purchased from commercial sources and used as received.…”

New Synthesis of 18-Norestradiol

“…82 (1999) The preparation of the corresponding phosphonium salt from 7 turned out to be a crucial step in this synthesis, since various commonly applied methods to substitute the primary bromide by PPh 3 failed. In solvents like benzene, toluene [13] or Et 2 O at elevated temperature (general method for the synthesis of (oxoalkyl)triphenylphosphonium bromide [14]), only tarry materials were recovered. However, melting at 858 a neat mixture of bromide 7 and PPh 3 (prepared by dissolving both components in abs.…”

75 Jahre Riechstoff‐ und Aroma‐Chemie im Spiegel der Helvetica Chimica Acta. Teil I

“…Die den Geruchscharakter des atherischen 01s von Opoponax bestimmende Verbindung erwies sich als (+)-(S,Z)-a -Bisabolen[37]. Fur die racemische Form der Stereoisomeren des CI -Bisabolens ist eine rationelle Synthese bekanntgeworden[38]. (-)-a -Bisabolol35, u. a. als Hauptprodukt des deutschen Kamillen-01s (45 "0) bekannt, tragt dort zur antiphlogistischen und spasmolytischen Aktivitat des atherischen 01s bei und fallt durch seinen angenehmen blumigen Geruch auf.…”