Säurekatalysierte Dienon-Phenol-Umlagerungen von 6-Propargyl-6-methyl-cyclohexa-2,4-dien-1-onen; ladungskontrollierte,aromatische [1s, 2s]- und [3s, 4s]-sigmatropische Reaktionen

The acid catalysed dienone-phenol rearrangement of methyl substituted o-propargyl-cyclohexadienones (scheme 3) was investigated. The rearrangements were carried out in acetic anhydride containing about 1⁰/₀₀ sulfuric acid. Under these conditions acetoxy benzenium ions are formed as intermediates. These then undergo charge-controlled [3s, 4s]- and [1s, 2s]-sigmatropic rearrangements. Thus, the [3s, 4s]-process leads to the formation of the corresponding allenyl-phenol acetates ( 19 , 21 , 23 , 25 , 28 , 30 ) whereas the [1s, 2s]-process yields propargyl-phenol acetates ( 20 , 22 , 24 , 26 , 29 ), respectively (cf. scheme 4).     

Dienol-Benzol-Umlagerung von Penta-2,4-dienyl-benzocyclohexadienolen

1-Hydroxy-2-methyl-2-(penta-2,4-dienyl)-1,2-dihydronaphthalene ( 2 ), on treatment with 0,75N H₂SO₄ in ether at 0°, underwent a [1s, 2s]-sigmatropic rearrangement to give 2-methyl-1-(penta-2,4-dienyl)-naphthalene ( 5 ), cf. scheme 2. 2-Hydroxy-1-methyl-1-(penta-2,4-dienyl)-1,2-dihydronaphthalene ( 4 ) under the same conditions gave 38% of the [1s, 2s]-product 1-methyl-2-(penta-2,4-dienyl)-naphthalene ( 6 ), together with 26% 1-methylnaphthalene, 21% 1-methyl-4-(penta-2,4-dienyl)-naphthalene ( 7 ) and 1% 1-methyl-5-(penta-2,4-dienyl)-naphthalene ( 8 ), cf. scheme 2. Most likely the latter two naphthalene derivatives at least are products of an intermolecular process.     

Zinkchloridkatalysierte,thermische Umlagerungen von N-Allyl in C-Allyl-aniline; ladungsinduzierte,aromatische Amino-Claisen-Umlagerungen

N-Allyl-2-methylaniline ( 12 ) forms on heating at 140° in xylene in the presence of zinc chloride 2-allyl-6-methylanline ( 19 ) as major compound and 4-allyl-2-methylaniline ( 20 ) as well as 2,7-dimethyl-indoline ( 21 ) as minor products. Compound 21 is also formed when 19 is heated in the presence of zinc chloride (scheme 2). That 19 arises from a charge-induced [3s, 3s] sigmatropic rearrangement of 12 – and 20 from two consecutive [3s, 3s]-sigmatropic transformations – follows from the reaction of N-crotyl-2-methylaniline ( 13 ) in the presence of zinc chloride at 140°. 2-(1′-Methylallyl)-6-methylaniline ( 22 ) and 4-crotyl-2-methylaniline ( 23 ) are formed exclusively. Small amounts of 2,3,7-trimethyl-indoline ( 24 ) and 2-(cis- and trans-1′-methyl-propenyl)-6-methylaniline (cis- and trans- 25 ) are observed as by-products. Compound 24 arises from 22 in the presence of zinc chloride (scheme 3). Similar results are obtained when N-allyl and N-(2′-methylallyl)-N-methyl-aniline ( 14 and 15 , respectively) are heated in the presence of zinc chloride. Whereas 14 gives nearly exclusively 2-allyl-N-methyl-aniline ( 28 ) and only small amounts of the corresponding 1, 2-dimethyl-indoline ( 29 ) and of 2-(cis- and trans-propenyl)-N-methyl-aniline (cis- and trans- 27 ), 15 forms comparable amounts of 2-(2′-methylallyl)-N-methyl-aniline ( 30 ), 1,2,2-trimethyl-indoline ( 31 ), and 2-isobutenyl-N-methyl-aniline ( 32 ) (scheme 4). Compound 30 , and also 32 , are transformed into 31 on heating in the presence of zinc chloride. Charge-induced aromatic amino-Claisen rearrangements are also observed when N-allylated anilinium tetraphenylborates are heated at 100–105° in hexamethyl phosphoric acid triamide. Thus, N-allyl- and N-crotyl-N, N-dimethyl-anilinium tetraphenylborate ( 16 and 17 , respectively) yield 2-allyl- and 2-(1′-methylallyl)-N,N-dimethyl-aniline ( 33 and 34 , respectively) besides small amounts of N, N-dimethyl-aniline. N-Cinnamyl-N, N-dimethyl-anilinium tetraphenylborate ( 18 ) gives, besides appreciable amounts of N,N-dimethyl-aniline, a mixture of 2-(1′-phenylallyl)-,2-cinnamyl-, and 4-cinnamyl-N, N-dimethyl-aniline ( 35 , 36 , and 37 , respectively) in which the first two compounds predominate.     

Reactions of 3-allyl-4-oxothieno[2,3-<Emphasis Type="Italic">d</Emphasis>]pyrimidin-2-yl disulfides with iodine

Reactions of 3-allyl-4-oxothieno[2,3-d]pyrimidin-2-yl disulfides with iodine afforded 2-iodomethyl-2,3-dihydrothieno[2,3-d][1,3]thiazolo[3,2-a]pyrimidin-5-ones. A probable mechanism of this transformation was theoretically justified. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2501–2504, November, 2005.     

The Reaction of 2-Ethoxy-3-Phenylbenzo[D]-1,3, 2-Oxazaphosphorin-6-One with α-Ketocarboxylic Acid Esters: Synthesis of Benzo[d]-1,3,2-Oxazaphosphepine Derivatives

Abstract

The reactions of 2-ethoxy-3-phenylbenzo[d]-1,3,2-oxazaphosphorin-6-one with R-carbonylcarboxylic acids ethyl esters (R = CF₃, Ph, and Me) lead to the formation of seven-membered heterocycles, 2-ethoxy-9-ethoxycarbonyl-2,8-dioxo-3-phenyl-9-R-benzo[d]-1,3,2-oxazaphosphepines.     

Degradative ring opening of pyrido and pyrazino 3-benzenesulfonyloxyuracils and their conversion to condensed pyrazolones and triazolones

Ring opening, followed by an immediate Lossen rearrangement, of 3-benzenesulfonyloxypyrido[3,2-d, 3,4-d and 4,3-d]pyrimidine-2,4(1H,3H)diones with sodium methoxide in methanol furnished good yields of the methyl esters of 3-[2-(methoxycarbonyl)hydrazino]-2-, 3-[2-(methoxycarbonylhydrazino]-4- and 4-[2-(methoxycarbonyl)hydrazino]-3-pyridinecarboxylic acids, respectively. These hydrazino esters were cyclized to the corresponding pyridopyrazolones. However, the reaction of 3-benzenesulfonyloxypyrido[2,3-d]pyrimidine-2,4(1H,3H)dione with sodium methoxide produced 8-methoxycarbonyl-s-triazolo[4,5-a]pyridin-3(2H)one. In similar fashion, sodium methoxide converted 3-benzenesulfonyloxylumazine to 8-methoxycarbonyl-s-triazolo[4,3-a]pyrazin-3(2H)one.     

1,3-Dipolar cycloadditions of diazoalkanes to pyridazine derivatives. Thermal 1,5-sigmatropic rearrangement of methyl groups in 3,3-dimethyl-3H-pyrazolo[3,4-d]pyridazine derivatives

Thermal 1,5-sigmatropic rearrangements of one of the methyl group attached at position 3 of 3,3-dimethyl-3H-pyrazolo[3,4-d]pyridazin-4(5H)-ones 1–3 taking place either in a clock-wise or anti-clockwise direction gave N₂-methylated products 4–6 and C_3a-methylated products 7– 9 . The -7(6)-one derivative 10 and -4,7(5H,6H)-dione derivative 12 gave only N₂-methylated products 11 and 13 respectively, and 1,2-dihydro derivative 14 produced after elimination of methane, 15 .     

Säurekatalysierte Umlagerung von Allyl-cyclohexadienon-tosyl-hydrazonen: Beispiel einer Dienimin-Anilin-Umlagerung

The tosylhydrazones of 4-allyl- and 4-crotyl-4-methyl-cyclohexa-2, 5-dien-l-one ( 14 and 15 ) rearrange in the presence of acid to yield the corresponding 2-allyl- and 2-α-methylallyl-hydrazines 17 and 18 , respectively. A similar behaviour is shown by the tosylhydrazone of 2-allyl-2-methyl-cyclohexa-3, 5-dien-1-one ( 16 ). 16 could not be isolated. The observed acidcatalysed [3 s, 3 s]-sigmatropic rearrangement of the tosylhydrazones can be regarded as a rearrangement of the dienimine-aniline type.     

Synthese und Röntgenstrukturanalyse von S4N4-Derivaten mit drei- und vierfach koordinierten Schwefelatomen

CF₃SO₂N?SCl₂ reagiert mit (CH₃)₂S[NSi(CH₃)₃]₂, (C₄H₈)S[NSi(CH₃)₃]₂ oder (C₅H₁₀)S[NSi(CH₃)₃]₂ unter Trimethylchlorsilanabspaltung zu den achtgliedrigen S₄N₄-Derivaten S₄N₄(NSO₂CF₃)₂(CH₃)₄ 3 , S₄N₄(NSO₂CF₃)₂(C₄H₈)₂ 4a und S₄N₄(NSO₂CF₃)₂(C₅H_{1 0})₂ 4b . In den achtgliedrigen SN-Ringen haben die Schwefelatome die Koordinationszahl 3 und 4. Die Röntgenstrukturanalyse von 4a ergab eine Sessel-Konformation. 4a kristallisiert orthorhombisch in der Raumgruppe Pna2₁ mit a = 17,641(4), b = 6,406(2), c = 19,130(4) Å, d_x = 1,815 g cm^?3 und Z = 4. Die mittleren S? N-Abstände betragen an den vierfach koordinierten Schwefelatomen 1,597 Å und an den Schwefelatomen mit der Koordinationszahl 3 1,650 Å. CF₃SO₂N? SCl₂ reagiert mit trimethylzinnhaltigen S? N-Verbindungen zum bekannten CF₃SO₂N[Sn(CH₃)₃]S(CH₃)NSO₂CF₃ und Dimethylzinndichlorid. Synthesis and X-Ray Structure Analysis of S₄N₄-Derivatives with Threefold and Fourfold Coordinated Sulfur Atoms CF₃SO₂N?SCl₂ reacts with (CH₃)₂S[NSi(CH₃)₃]₂, (C₄H₈)S[NSi(CH₃)₃]₂ or (C₅H₁₀S[NSi(CH₃)₂]₂ under elimination of (CH₃)₃SiCl to yield the eight-membered S₄N₄ derivatives S₄N₄?NSO₂CF₃)₂(CH₃)₄, 3 , S₄N₄(NSO₂CF₃)₂(C₄H₈)₂ 4a und S₄N₄(NSO₂CF₃)₂(C₅H_{1 0})₂ 4b . In the eight-membered SN-rings the sulfur atoms have the coordination number 3 and 4. The X-ray structure analysis of 4a revealed a chair conformation. 4a crystallizes in the orthorhombic space group Pna2₁ with a = 17.641(4), b = 6.406(2), c = 19.130(4) Å, d_x = 1.815 g cm^?3, and Z = 4. The average S? N distance was found to be 1.597 Å at fourfold coordinated sulfur atoms and 1.650 Å at sulfur with coordination number 3. CF₃SO₂N=SCl₂ reacts with trimethyl tin-containing S? N compounds to the known CF₃SO₂N[Sn(CH₃)₃]S(CH₃)NSO₂CF₃ and dimethyl tin dichloride.     

Synthesis and structural characterisation of gallium and indium fluoroalkoxide ‘ate’ complexes

The treatment of InCl₃ with MOCH(CF₃)₂ (M = Li, Na, K) in a 1:6 stoichiometry, followed by recrystallisation results in the formation of the bimetallic “ate” complexes [Na₃In(OCH(CF₃)₂)₆(THF)₃] (2) and [Li₃In(OCH(CF₃)₂)₆(THF)₃] (5) from hexane, and [K₃In(OCH(CF₃)₂)₆]_n (4) from a THF and toluene mixture. If a 1:3 stoichiometry is used chloride containing compounds [Na₂InCl(OCH(CF₃)₂)₄(THF)₄] (1) and [KInCl₂ (OCH(CF₃)₂)₂(THF)₃]_n · THF (3) are obtained on recrystallisation from hexane. Treatment of GaCl₃ with 6 equivalents of LiOC(CH₃)₂CF₃ gives [LiGa(OC(CH₃)₂CF₃)₄(THF)₂] (6) on recrystallisation from hexane. The protolysis reaction between In(N(SiMe₃)₂)₃, formed in situ from (Me₃Si)₂NH, ⁿBuLi and Incl₃, and HOCH(CH₃)CF₃ results in isolation of [LiIn(OCH(CH₃)CF₃)₃Bu]₂ (7) from hexane. The structures of 2, 4, and 5 all contain the tetranuclear core InO₆M₃. Compounds 1 and 3 have residual chloride; 1 is a trinuclear species with two THF ligands per Na, while 3 is a linear polymer. Compound 6 has a GaO₂Li four-membered parallelogram at its core. Complex 7 has a tetranuclear In₂O₆Li₂ core and an unexpected ⁿBu group on the In atoms. The coordination spheres of the alkali metals in 1-6 include solvated THF while 1-5 display additional close M?F interactions.     

Synthesis of nitrogen-containing drimane sesquiterpenoids from 11-dihomodrim-8(9)-en-12-one

Products from the reaction of 11-dihomodriman-8α-ol-12-one with several reagents such as MeSO₃SiMe₃, CF₃SO₃SiMe₃, Sc(CF₃SO₃)₃, conc. H₂SO₄ in EtOH (30% solution), and Amberlist-15 ion-exchange resin were studied. 11-Dihomodrim-8(9)-en-12-one and its oxime were synthesized. The reaction of its oxime with H₃PO₄ (86%) or CF₃CO₂H produced (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho [1,2-e]-3-methyl-4,5-dihydro-[1,2,6]-oxazine; with p-TsCl in Py, (1S,2S,4aS,8aS)-2,5,5,8a-tetramethyldecahydro-1H-naphtho[1,2-d]-2-methylpyrroline-N-oxide; and with PCl₅ in Et₂O, 11-acetylaminodrim-8(9)-ene and 11-methylaminooxodrim-8(9)-ene.     

Umlagerungsreaktionen von (2′-Propinyl)cyclohexadienolen und -semibenzolen

Rearrangements of (2′-Propinyl)cyclohexadienols and -semibenzenes The acid-catalyzed dienol-benzene rearrangement of 3- and 5-methyl-substituted (2′-propinyl)cyclohexadienols has been investigated. Treatment of the dienols with CF₃COOH in CCl₄ yields allenyl- and (2′-propinyl)benzenes via [3,4]- and [1,2]-sigmatropic rearrangements, respectively. The reaction with H₂SO₄ in Et₂O leeds to a mixture of allenyl-, 2′-propinyl-, 3′-butinyl- and (2′,3′-butadienyl)benzenes (Scheme 3). The latter are products of a thermal semibenzene-benzene rearrangement (cf. Scheme 9). The corresponding semibenzenes have been prepared by dehydration of the cyclohexadienols with H₂SO₄ or POCl₃ (Schemes 6 and 7). Under acidic conditions, the p-(2′-propinyl)semibenzenes 33–35 (Scheme 8) undergo [3,4]- and [1,2]-sigmatropic rearrangements to give again allenyl- and (2′-propinyl)benzenes, whereas the thermal rearrangements to the 3′-butinyl- and (2′,3′-butadienyl)benzenes (Scheme 9) involves a radical mechanism. In contrast, the o-(2′-propinyl)semibenzene b (Scheme 7) leads to (2′,3′-butadienyl)benzene 32 via a thermal [3,3]-sigmatropic rearrangement.     

Synthesen und NMR‐Untersuchungen von Salzen mit den neuen Anionen [PtXn(CF3)6‐n]2— (n = 0 ‐ 5, X = F,OH, Cl,CN) und die Kristallstrukturanalyse von K2[(CF3)2F2Pt(μ‐OH)2PtF2(CF3)2]·2H2O

Syntheses and NMR Spectroscopic Ivestigations of Salts containing the Novel Anions [PtX_n(CF₃)_6‐n]^2— (n = 0 ‐ 5, X = F, OH, Cl, CN) and Crystal Structure of K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O The first syntheses of trifluoromethyl‐complexes of platinum through fluorination of cyanoplatinates are reported. The fluorination of tetracyanoplatinates(II), K₂[Pt(CN)₄], and hexacyanoplatinates(IV), K₂[Pt(CN)₆], with ClF in anhydrous HF leads after working up of the products to K₂[(CF₃)₂F₂Pt(μ‐OH)₂PtF₂(CF₃)₂]·2H₂O. The structure of the salt is determined by a X‐ray structure analysis, P2₁/c (Nr. 14), a = 11.391(2), b = 11.565(2), c = 13.391(3)Å, β = 90.32(3)°, Z = 4, R₁ = 0.0326 (I > 2σ(I)). The reaction of [Bu₄N]₂[Pt(CN)₄] with ClF in CH₂Cl₂ generates mainly cis‐[Bu₄N]₂[PtCl₂(CF₃)₄] and fac‐[Bu₄N]₂[PtCl₃(CF₃)₃], but in contrast that of [Bu₄N]₂[Pt(CN)₆] with ClF in CH₂Cl₂ results cis‐[Bu₄N]₂[PtX₂(CF₃)₄], [Bu₄N]₂[PtX(CF₃)₅] (X = F, Cl) and [Bu₄N]₂[Pt(CF₃)₆]. In the products [Bu₄N]₂[PtX_n(CF₃)_6‐n] (X = F, Cl, n = 0—3) it is possibel to exchange the fluoro‐ligands into chloro‐ and cyano‐ligands by treatment with (CH₃)₃SiCl und (CH₃)₃SiCN at 50 °C. With continuing warming the trifluoromethyl‐ligands are exchanged by chloro‐ and cyano‐ligands, while as intermediates CF₂Cl and CF₂CN ligands are formed. The identity of the new trifluoromethyl‐platinates is proved by ¹⁹⁵Pt‐ and ¹⁹F‐NMR‐spectroscopy.     

General Assembly of Twisted Trigonal‐Prismatic Nonanuclear Silver(I) Clusters

A general class of C₃‐symmetric Ag₉ clusters, [Ag₉S(tBuC₆H₄S)₆(dpph)₃(CF₃SO₃)] ( 1 ), [Ag₉(tBuC₆H₄S)₆(dpph)₃(CF₃SO₃)₂] ? CF₃SO₃ ( 2 ), [Ag₉(tBuC₆H₄S)₆(dpph)₃(NO₃)₂] ? NO₃ ( 3 ), and [Ag₉(tBuC₆H₄S)₇(dpph)₃(Mo₂O₇)_0.5]₂ ? 2 CF₃COO ( 4 ) (dpph=1,6‐bis(diphenylphosphino)hexane), with a twisted trigonal‐prism geometry was isolated by the reaction of polymeric {(HNEt₃)₂[Ag₁₀(tBuC₆H₄S)₁₂]}_n, 1,6‐bis(diphenylphosphino)hexane, and various silver salts under solvothermal conditions. The structures consist of discrete clusters constructed from a girdling Ag₉ twisted trigonal prism with the top and bottom trigonal faces capped by diverse anions (i.e., S^2? and CF₃SO₃^? for compound 1 , 2×CF₃SO₃^? for compound 2 , 2×NO₃^? for compound 3 , and tBuC₆H₄S^? and Mo₂O₇^2? for compound 4 ). This trigonal prism is bisected by another shrunken Ag₃ trigon at its waist position. Interestingly, two inversion‐related Ag₉ trigonal‐prismatic clusters are dimerized by the Mo₂O₇^2? ion in compound 4 . The twist is amplified by the bulkier thiolate, which also introduces high steric‐hindrance for the capping ligand, that is, the longer dpph ligand. Four more silver–sulfur clusters (namely, compounds 5 – 8 ) with their nuclearity ranging from 6–10 were solely characterized by single‐crystal X‐ray diffraction to verify the above‐described synergetic effect of mixed ligands in the construction of Ag₉ twisted trigonal prisms. Surprisingly, only cluster 1 emits yellow luminescence at λ=584 nm at room temperature, which may be attributed to a charge transfer from the S 3p orbital to the Ag 5s orbital, or mixed with metal‐centered (MC) d¹⁰→d⁹s¹ transitions. Upon cooling from 300 to 80 K, the emission intensity was enhanced along with a hypsochromic shift. The good linear relationship between the maximum emission intensity and the temperature for compound 1 in the range of 180–300 K indicates that this is a promising molecular luminescent thermometer. Furthermore, cyclic voltammetric studies indicated that the diffusion‐ and surface‐controlled redox processes were determined for compounds 1 and 3 as well as compound 4 , respectively.     

Syntheses and properties of cyanamide and cyanoguanidine complexes of platinum(II). X-Ray structure of trans-[Pt(CF3)(NCNEt2)(PPh3)2][BF4]

Complexes trans-[PtX(L)(PPh₃)₂]A [1: X = CF₃; A = BF₄; L = NCNH₂, NCNMe₂, NCNEt₂, or NCNC(NH₂)₂. 2: X = Cl; A = BPh₄; L = NCNMe₂ or NCNEt₂] and cis-[PtCl(L)(PPh₃)₂][BPh₄] [3: L = NCNH₂ or NCNC(NH₂)₂], which appear to be the first cyanamide or cyanoguanidine complexes of platinum to be reported, have been prepared by treatment of trans-[PtBr(CF₃)(PPh₃)₂] (in CH₂Cl₂/acetone and in the presence of Ag[BF₄]) or of cis-[PtCl₂(PPh₃)₂] (in THF and in the presence of Na[BPh₄]), respectively, with the appropriate substrate. In KBr pellets or in solution 1 (L = NCNMe₂ or NCNEt₂) undergoes ready replacement of the organocyanamide (under the trans influence of CF₃) by bromide to regenerate trans-(PtBr(CF₃)(PPh₃)₂]. The X-ray structure of 1 (X = CF₃, A = BF₄, L = NCNEt₂) is also reported, and shows the presence of two apical intramolecular contacts of the metal with two ortho-hydrogen atoms of the phosphines, whereas the amine N atom of the diethylcyanamide is trigonal planar in the linear NCN framework with a delocalized π system.     

A new approach to the synthesis of trifluoromethylated products of the [3,3]-sigmatropic rearrangement

CH-acids of general formula CF₃CH(X)CF₃ (X = CF₃, CO₂R) react with 2,3-unsaturated alcohols in the presence of bases to give trifluoromethylated products of the [3,3]-sigmatropic rearrangement. These reactions provide a convenient method for the synthesis of 2-alkenyl-2-trifluoromethylmalonates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1273–1277, July, 1994.     

Breaking and Making of Carbon–Carbon Bonds by Lanthanides and Third‐Row Transition Metals

Carbon‐atom extrusion from the ipso‐position of a halobenzene ring (C₆H₅X; X=F, Cl, Br, I) and its coupling with a methylene ligand to produce acetylene is not confined to [LaCH₂]⁺; also, the third‐row transition‐metal complexes [MCH₂]⁺, M=Hf, Ta, W, Re, and Os, bring about this unusual transformation. However, substrates with substituents X=CN, NO₂, OCH₃, and CF₃ are either not reactive at all or give rise to different products when reacted with [LaCH₂]⁺. In the thermal gas‐phase processes of atomic Ln⁺ with C₇H₇Cl substrates, only those lanthanides with a promotion energy small enough to attain a 4fⁿ5d¹6s¹ configuration are reactive and form both [LnCl]⁺ and [LnC₅H₅Cl]⁺. Branching ratios and the reaction efficiencies of the various processes seem to correlate with molecular properties, like the bond‐dissociation energies of the C?X or M⁺?X bonds or the promotion energies of lanthanides.     

Influence of Ring Annelation on the Mode Selectivity of the Ionized Diazabicycloheptenes and Corresponding Housanes: An ESR and ENDOR Study

The tricyclic azoalkanes, (1α,4α,4aα,7aα)‐4,4a,5,6,7,7a‐hexahydro‐1,4,8,8‐tetramethyl‐1,4‐methano‐1H‐cyclopenta[d]pyridazine ( 1c ), (1α,4α,4aα,6aα)‐4,4a,5,6,6a‐pentahydro‐1,4,7,7‐tetramethyl‐1,4‐methano‐1H‐cyclobuta[d]pyridazine ( 1d ), (1α,4α,4aα,6aα)‐4,4a,6a‐trihydro‐1,4,7,7‐tetramethyl‐1,4‐methano‐1H‐cyclobuta[d]pyridazine ( 1e ), and (1α,4α,4aα,5aα)‐4,4a,5,5a‐tetrahydro‐1,4,6,6‐tetramethyl‐1,4‐methano‐1H‐cyclopropa[d]pyridazine ( 1f ), as well as the corresponding housanes, the 2,3,3,4‐tetramethyl‐substituted tricyclo[3.3.0.0^2,4]octane ( 2c ), tricyclo[3.2.0.0^2,4]heptane ( 2d ), and tricyclo[3.2.0.0^2,4]hept‐6‐ene ( 2e ), were subjected to γ‐irradiation in Freon matrices. The reaction products were identified with the use of ESR and, in part, ENDOR spectroscopy. As expected, the strain on the C‐framework increases on going from the cyclopentane‐annelated azoalkanes and housanes ( 1c and 2c ) to those annelated by cyclobutane ( 1d and 2d ), by cyclobutene ( 1e and 2e ), and by cyclopropane ( 1f ). Accordingly, the products obtained from 1c and 2c in all three Freons used, CFCl₃, CF₃CCl₃, and CF₂ClCFCl₂, were the radical cations 3c ^.+ and 2c ^.+ of 2,3,4,4‐tetramethylbicyclo[3.3.0]oct‐2‐ene and 2,3,3,4‐tetramethylbicyclo[3.3.0]octane‐2,4‐diyl, respectively. In CFCl₃ and CF₃CCl₃ matrices, 1d and 2d yielded analogous products, namely the radical cations 3d ^.+ and 2d ^.+ of 2,3,4,4‐tetramethylbicyclo[3.2.0]hept‐2‐ene and 2,3,3,4‐tetramethylbicyclo[3.2.0]heptane‐2,4‐diyl. The radical cations 3c ^.+ and 3d ^.+ and 2c ^.+ and 2d ^.+ correspond to their non‐annelated counterparts 3a ^.+ and 3b ^.+, and 2a ^.+ and 2b ^.+ generated previously under the same conditions from 2,3‐diazabicyclo[2.2.1]hept‐2‐ene ( 1a ) and bicyclo[2.1.0]pentane ( 2a ), as well as from their 1,4‐dimethyl derivatives ( 1b and 2b ). However, in a CF₂ClCFCl₂ matrix, both 1d and 2d gave the radical cation 4d ^.+ of 2,3,3,4‐tetramethylcyclohepta‐1,4‐diene. Starting from 1e and 2e , the radical cations 4e ^.+ and 4e′ ^.+ of the isomeric 1,2,7,7‐ and 1,6,7,7‐tetramethylcyclohepta‐1,3,5‐trienes appeared as the corresponding products, while 1f was converted into the radical cation 4f ^.+ of 1,5,6,6‐tetramethylcyclohexa‐1,4‐diene which readily lost a proton to yield the corresponding cyclohexadienyl radical 4f ^.. Reaction mechanisms leading to the pertinent radical cations are discussed.     

Chiral Fluorinated α‐Sulfonyl Carbanions: Enantioselective Synthesis and Electrophilic Capture,Racemization Dynamics,and Structure

Enantiomerically pure triflones R¹CH(R²)SO₂CF₃ have been synthesized starting from the corresponding chiral alcohols via thiols and trifluoromethylsulfanes. Key steps of the syntheses of the sulfanes are the photochemical trifluoromethylation of the thiols with CF₃Hal (Hal=halide) or substitution of alkoxyphosphinediamines with CF₃SSCF₃. The deprotonation of RCH(Me)SO₂CF₃ (R=CH₂Ph, iHex) with nBuLi with the formation of salts [RC(Me)? SO₂CF₃]Li and their electrophilic capture both occurred with high enantioselectivities. Displacement of the SO₂CF₃ group of (S)‐MeOCH₂C(Me)(CH₂Ph)SO₂CF₃ (95 % ee) by an ethyl group through the reaction with AlEt₃ gave alkane MeOCH₂C(Me)(CH₂Ph)Et of 96 % ee. Racemization of salts [R¹C(R²)SO₂CF₃]Li follows first‐order kinetics and is mainly an enthalpic process with small negative activation entropy as revealed by polarimetry and dynamic NMR (DNMR) spectroscopy. This is in accordance with a C_α? S bond rotation as the rate‐determining step. Lithium α‐(S)‐trifluoromethyl‐ and α‐(S)‐nonafluorobutylsulfonyl carbanion salts have a much higher racemization barrier than the corresponding α‐(S)‐tert‐butylsulfonyl carbanion salts. Whereas [PhCH₂C(Me)SO₂tBu]Li/DMPU (DMPU = dimethylpropylurea) has a half‐life of racemization at ?105 °C of 2.4 h, that of [PhCH₂C(Me)SO₂CF₃]Li at ?78 °C is 30 d. DNMR spectroscopy of amides (PhCH₂)₂NSO₂CF₃ and (PhCH₂)N(Ph)SO₂CF₃ gave N? S rotational barriers that seem to be distinctly higher than those of nonfluorinated sulfonamides. NMR spectroscopy of [PhCH₂C(Ph)SO₂R]M (M=Li, K, NBu₄; R=CF₃, tBu) shows for both salts a confinement of the negative charge mainly to the C_α atom and a significant benzylic stabilization that is weaker in the trifluoromethylsulfonyl carbanion. According to crystal structure analyses, the carbanions of salts {[PhCH₂C(Ph)SO₂CF₃]Li? L }₂ ( L =2 THF, tetramethylethylenediamine (TMEDA)) and [PhCH₂C(Ph)SO₂CF₃]NBu₄ have the typical chiral C_α? S conformation of α‐sulfonyl carbanions, planar C_α atoms, and short C_α? S bonds. Ab initio calculations of [MeC(Ph)SO₂tBu]^? and [MeC(Ph)SO₂CF₃]^? showed for the fluorinated carbanion stronger n_C→σ* and n_O→σ* interactions and a weaker benzylic stabilization. According to natural bond orbital (NBO) calculations of [R¹C(R²)SO₂R]^? (R=tBu, CF₃) the n_C→σ*_{S? R} interaction is much stronger for R=CF₃. Ab initio calculations gave for [MeC(Ph)SO₂tBu]Li ? 2 Me₂O an O,Li,C_α contact ion pair (CIP) and for [MeC(Ph)SO₂CF₃]Li ? 2 Me₂O an O,Li,O CIP. According to cryoscopy, [PhCH₂C(Ph)SO₂CF₃]Li, [iHexC(Me)SO₂CF₃]Li, and [PhCH₂C(Ph)SO₂CF₃]NBu₄ predominantly form monomers in tetrahydrofuran (THF) at ?108 °C. The NMR spectroscopic data of salts [R¹(R²)SO₂R³]Li (R³=tBu, CF₃) indicate that the dominating monomeric CIPs are devoid of C_α? Li bonds.