„Push‐pull”︁‐substituierte Allene, IV. Synthese und Eigenschaften o‐chinoider Donor/Akzeptorsubstituierter Allene Kristall‐ und Molekülstruktur von E‐2,2,2′,2′‐Tetraethoxy‐Δ^{3,3′(2H,2′H)}‐bi[phenanthro[9,10‐b]furan]

Abstract

Bei der Umsetzung des (2,2-Diethoxyvinyliden)triphenylphosphorans (7) mit den o-Chinonen 6 entstehen uber die Oxaphosphetane 8 intermediar die Donor/Akzeptor-Allene 9. Diese gehen in die Carbene 10 uber, die dann spontan zu den Olefinen 11 dimerisieren. Die Temperaturabhangigkeit der 'H-NMR-Spektren liefert Einblick in die Diastereomerisierung der verdrillten Olefine 11 b und die konformative Beweglichkeit des E-Isomeren. Die saure Hydrolyse der Z/E-isomeren Orthoester lla fuhrt uber das Monolacton 12 zu dem Bislacton 13. Die Monomeren 9/10 lassen sich mit Triphenylphosphan unter Bildung der Orthoester-phosphorane 14 abfangen, die sich durch Elirninierung von Ether zu den Phosphoranen 16 stabilisieren. Die Struktur des E-Dimeren 11 b wurde rontgendiffraktometrisch bestimmt. Push-pull Substituted Allenes, IV l) Synthesis and Properties of o-Quinoid Donor/Acceptor Substituted Allenes Crystal-and Molecule Structure of E-2,2,2',2'-Tetraethoxy-A3~3'~'H~z'H)-bi[phenanthro[9,lO-b]furan]Reaction of the (2,2-diethoxyvinylidene)triphenylphosphorane (7) with the o-quinones 6 yields the donor/acceptor allene intermediates 9 via the oxaphosphetanes 8. The allenes 9 give the carbenes 10 which then spontaneously dimerize forming the olefins 11. The temperature dependence of the 'H NMR spectra leads to insights into the diastereomerization of the torsionally distorted olefins l i b and the conformational mobility of the E-isomer. Acidic hydrolysis of the Z/E-isomeric orthoesters 11 a leads to the monolactone 12 and the bislactone 13. The monomers 9/10 can be trapped by triphenylphosphane affording the orthoester-phosphoranes 14 which under elimination of ether give the phosphoranes 16. The structure of the E-dimer 11 b has been determined from X-ray data.Ersetzt man in einem ambiphilen Carben 1 2, den Donorsubstituenten (Do) durch ein stabilisiertes Anion und den Akzeptorsubstituenten (A) durch ein stabilisiertes Kation, so gelangt man zu einem dipolaren Carben 2, das man auch als Allen 3 betrachten

Radicals and Polymers

“…Its tentative mechanism involves the dehy drochlorination of the 3chlorobenzofu ranone 52 to afford the carbene 53 and its dimerization to yield 55. Similar 5,7di-tbutyl2,2diethoxy3Hbenzofuranyl carbene and its dimerization, followed by hydrolysis leading to 55 was reported [78] by Saalfrank, Böhme and coworkers. However, a later work by Kresge, Wirz and coworkers [79] showed that the carbene derived from 3diazobenzofuran2one is very shortlived and undergoes rapid ring opening to 6(oxoethenylidene)2,4cyclo hexadien1one, the actual species dimer izing to the (unsubstituted) isoxindigo.…”

Reactions of ortho-quinones with ethoxycarbonylmethylene(triphenyl)-phosphorane. Trapping of the ortho-quinone methanide intermediates

“…6143°C (from hexane) (Found: C, 43.5; H, 2.9. C16H14C1406 requires C, 43.27; H, 3.18%); v,,,(Nujol) 1 790, 1 735, 1 725, and 1 655 cm-'; 6 , ( 8 0 s), 4.07 (2 H, q, J 7 Hz), 4.24 (2 H, q, J 7 Hz), and 7.14 (1 H, s); m/z 448 ( M + , 0.3%), 446 (M', l), 444 (M', 1.6), 442 (M', lS), 411 (4), 409 (12), 407 (13), 404 (2), 402 (3), 400 (2), 369 (21), 367 (60), 365 (67), 285 (48), 283 (loo), 281 (85), 256 (62), and 254 (48).…”

Synthesis with Perfect Atom Economy: Generation of Furan Derivatives by 1,3-Dipolar Cycloaddition of Acetylenedicarboxylates at Cyclooctynes

“…These intermediates can be trapped by molecules with electron-deficient π-systems to give complex polycyclic products through a cascade of cycloaddition reactions. On the other hand, interception of 2 in the presence of protic reaction partners leads to 2,3-dihydrofuran derivatives with the rare substitution pattern of an orthoester functionality and a 3-methylidene group [36,37,38]. In all cases, the products are formed with perfect atom economy, that means that all atoms of the substrate molecules are found in the product.…”

“…To the best of our knowledge, this rare substitution pattern is found in a few compounds only, see ref. [37,38]. …”