η⁶‐(1,2‐Dioxocyclobutabenzol)tricarbonylchrom(O): Edukt für doppelt anionische Oxy‐Cope‐Umlagerungen unter besonders milden Bedingungen

Abstract

Nature 1991,353, 642-644. Analytisch reine Proben erhllt man durch einfache Filtration, anschlie-Bendes Waschen mit wasserfreiem EtOH und MeCN und Trocknen im Vakuum bei 100°C fur 2-6 h. Korrekte C,H,Ba,Si-Analyse fur 1 '3.25 HOCH,CH,OH. Kristalldaten fur 1 . 3.25 HOCH,CH,OH: triklin P i , a =10.151(8), b = 13.865(5), c = 15.709(6) A, C( = 102.90(3), / l = 91.04(3), y = 109.75(3)", V = 2018(1)A3,Z= 4,eb,, =1.70gcm~',p(MoK.) = 2.08mm-',F(000) = 1080, farbloses rechteckiges Pllttchen, 0.2 x 0.5 x 0.44 mm3, 13038 Reflexe gemessen mit 5" < 28 < 50", 9298 unabhdngige Reflexe, R,,, = 0.0312; 8999 Reflexe mit Fo 2 6a(F) verfeinert. Die Daten wurden auf einem rnit LT-2-Tieftemperatureinrichtung ausgestatteten Siemens-R3/v-Diffraktometer bei 175 K gesammelt, mit Absorptions-(4-Scans) und Sekundare-Extinktions-Korrektur. Die Struktur wurde mit Direkten Methoden gelost, mit Siemens-SHELXTL-PLUS-Programm verfeinert. Alle Nicht-H-Atome wurden anisotrop verfeinert, die H-Atome wurden mit Differenz-Fourier-Synthese lokalisiert und isotrop verfeinert. Das 0-Atom eines Kristallsolvens-Glycolmolekuls ist auf zwei Lagen fehlgeordnet mit verfeinerten Besetzungszahlen von 0.700(1) und 0.300(1). Das entsprechende H-Atom wurde nicht eingesetzt. 745 Parameter mit [w-' = a2(F) + 0.000382(F,)2] verfeinert, R = 0.0282, R, = 0.0374, Restelektronendichte maximal + 0.80 e A-3, minimal -0.82 e k 3 .Weitere Einzelheiten zur Kristallstrukturuntersuchung konnen beim Direktor des Cam-

The First Anionic Thia‐Fries Rearrangements at Ferrocene: Ready Access to Trifluoromethylsulfonyl‐Substituted Hydroxyferrocenes and an Extremely High Interannular Stereoinduction between Cyclopentadienyl Ligands

“…After phase separation the organic layer was collected with a syringe and filtered into a Schlenk flask through a P4 frit covered with a 5 cm thick layer of MgSO 4 . After solvent removal 2,5-bis(trifluoromethylsulfonyl)ferrocenol (14) was isolated as an orange solid; yield: 2.00 g (17) 1-Methoxy-2,5-bis(trifluoromethylsulfonyl)ferrocene (15) At À78 8C LDA in THF [prepared from 1.6 M n-BuLi (2.7 mL, 4.4 mmol) in hexane and diisopropylamine (1.9 mL, 13.2 mmol) in THF (20 mL)] was added dropwise over 40 min to 2-(trifluoromethylsulfonyl)ferrocenyl triflate (13, 1.8 g, 4.4 mmol) in THF (20 mL). The color changed from light yellow to deep red.…”

“…[13] In contrast, there is strong mass spectrometric evidence for the (benzyne)Cr + cation with the chromium atom attached at the cyclic p system. [14] As a matter of fact, the respective MS peak at m/z = 128 is the base peak in mass spectra of tricarbonylchromium complexes of benzocyclobutenedione, [14,15] indantrione, [16] indan-1,3-dione, [16] and acetals thereof as a result of fragmentation reactions. These findings caused our interest in the synthesis or trapping of p complexes of arynes and related systems.…”

Synthesis of Enantiopure Tricarbonyl(indan‐1,2‐dione)chromium

“…The reaction sequence proved to be highly diastereoselective and makes highly substituted polycyclic systems available in a very efficient way. [22,23,[33][34][35][36][37][61][62][63] It was also shown that the vinyllithium diaddition followed by a dianionic oxy-Cope rearrangement works with uncoordi- nated indan-1,2-dione, albeit in only moderate yield. [64] We envisaged the possibility that the electron withdrawal from the tricarbonylchromium group in 5 might help to improve the allkenyllithium diaddition yield and thereby allow the rearrangement to take place with better overall yield.…”

“…[14][15][16][17][18][19][20][21] We have contributed to this development in our investigations in the field of (arene)tricarbonylchromium complexes with functionalized anellated rings. [22][23][24] Key compounds in our research are complexes 1-4 of benzocyclobutenone, [22,[25][26][27][28][29][30][31] benzocyclobutenedione, [27,29,30,[32][33][34][35][36][37] 1,3-indandione, [38] and 1,2,3-indantrione. [38] In particular, chemistry relating to 1 and 2 has unveiled important oxy anion-accelerated reactions, such as anionic ring-opening reactions or dianionic oxyCope rearrangements, which take place under particularly mild reaction conditions.…”

Cascade Rearrangements Following Twofold Addition of Alkenyl Anions to Squarate Esters

“…When 2 equiv. of vinyllithium are added to (benzocycloThe twofold addition of organometallics to squarate esters had not been extensively examined at the time that our butenedione)tricarbonylchromium, the double addition occurs in cis fashion because of steric constraints [26] . Distudies were initiated.…”