Organische Fluorverbindungen, IV¹⁾. Carbonyl‐Fluorolefinierungen

Abstract

Eingegangen am 31. Oktober 1963Bromfluoressigsaureathylester und Triathylphosphit geben bei 150 -160" eine Amusow-Reaktion unter Bildung von Carbathoxyfluormethyl-phosphonsaurediathylester, dessen Carbanion XI11 rnit Aldehyden zu cis-und mit Ketonen zu a.P-ungesattigten cis-+ trans-a-Fluor-carbonsaureestern reagiert. Durch Reduktion mit LiAIH4 werden hieraus Fluorisoprenole erhalten. Andere Verfahren zur Darstellung dieser Fluorolefine durch Verwendung von Fluoroxalessigsaureester (iiber P-Fluor-a-keto-y-lacton-P-carbonsaureester) oder Bromfluoressigsaureester (iiber a-Fluor-P-hydroxy-carbonsaureester) werden besprochen.Die Synthese Fluor-substituierter Isoprenoide gelingt durch Carbonyl-Olefinierung geeigneter Fluorketonez). Der induktive Effekt des Fluorsubstituenten (oI = +0.52)3) kann AnlaB zu abweichenden Wirkungen biologisch aktiver Isoprenoide geben4). Gleiches Interesse beanspruchen Isoprenoide rnit olefinisch gebundenem Fluor. Der F-Substituent kann neben dem induktiven einen ausgepragten Resonanzeffekt ((zR = -0.40)3) auf x-Elektronensysteme ausiiben. Fluorisoprenoide dieses Typs sollten durch Reaktion geeigneter C3-, c8-oder C13-Ketone rnit F-haltigen C2-Komponenten zuganglich sein.

Aristolochene Synthase‐Catalyzed Cyclization of 2‐Fluorofarnesyl‐Diphosphate to 2‐Fluorogermacrene A

“…We have therefore studied the AS-catalyzed reaction of 2-fluorofarnesyldiphosphate (1 b), which was prepared by using a modification of a published procedure. [11] Geranyl acetone was treated with triethyl 2-fluoro-2-phosphonoacetate and sodium hydride, followed by DIBAL-H reduction of the resulting ester mixture to give 9 and 10 in a ratio of approximately 1:1 (Scheme 2). Bromination of 10 followed by diphosphorylation [12] and purification by reversed-phase HPLC gave 1 b in 36 % yield over these two steps.…”

Synthetic Methods for Fluorinated Olefins

“…(1-Fluorovinyl)methyldiphenylsilane (54) can be easily prepared by treatment of 1,1-difluoroethylene (35) with Ph 2 MeSiLi in THF (Scheme 41). [71] In the presence of Pd(PPh 3 ) 4 , CuI, and CsF, cross-coupling between 54 and aryl iodides smoothly proceeds to give fluorostyrene products in good to excellent yields. Compound 54 can be easily converted into 1-fluorovinylstannane 53b, which serves as a good substrate in Pd-catalyzed cross-coupling protocols.…”

Stereoselective Synthesis of Tetrasubstituted (Z)-Alkenes from Aryl Alkyl Ketones Utilizing the Horner-Wadsworth-Emmons Reaction.

“…We have recently reported a new approach to the stereoselective HWE reaction of methyl bis(2,2,2-trifluoroethyl)-phosphonoacetate (1) 2) or ethyl 2-fluoro-2-diethylphosphonoacetate 3) with aryl alkyl ketones by using Sn(OSO 2 CF 3 ) 2 and N-ethylpiperidine. [4][5][6][7][8] While a number of methods have been developed for the stereoselective synthesis of alkenes, few accounts have appeared in the literature describing the convenient preparation of tetrasubstituted (Z )-alkenes with excellent selectivity.…”