Facile hydrometalation of alkynes by nido-1,2-(CpRuH)(2)B(3)H(7) yielding novel Ru-B edge-bridging alkylidenes. Stepwise conversion of HCtbd1;CC(O)OMe into nido-1,2-(CpRuH)(2)-3-HOB-4-MeC-5-MeOC-BH(3), Cp = eta(5)-C(5)Me(5)

The reaction of the alkyne HCCC(O)OMe with 7 sep 1,2-(Cp*RuH)2B3H7 leads to hydroboration plus hydroruthenation to produce nido-1,3-mu-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7, a compound with an exocluster ruthenium-boron mu-alkylidene that exists in two isomeric forms. Both isomers undergo rearrangement with intramolecular chelation of the carbonyl oxygen at a boron site, thereby opening the cluster and generating arachno-2,3,-mu(C)-5-eta1(O)-Me{C(O)OMe}C-1,2-(Cp*Ru)2B3H7. Further heating leads to deoxygenation of the carbonyl fragment by a boron center concurrent with insertion of the carbon atom into the metallaborane cage to give nido-1,2-(Cp*RuH)2-3-HOB-4-MeC-5-MeOC-BH3.     

Thermodynamics of vinyl ethers—XVII : Thermodynamic stability of 1,2-dialkoxyethylenes

The relative thermodynamic stability of the monoalkoxy- and 1,2-dialkoxyethylene systems [OCCH(C) and OCCO, respectively] has been studied by chemical equilibration of suitable isomeric compounds. Although a single alkoxy substituent stabilizes the CC bond by about 25 kJ mol^?1, the 1,2-dialkoxyethylene system is no more stable than the monoalkoxyethylene (“ordinary” vinyl ether) system. On the contrary, the MeOCCOMe system was found to be about 4 kJ mol^?1 (on an enthalpy basis) less stable than the system MeOCCH.     

Doubly hydrogen-bridged 1,2-diphenylenediboranes derived from 9-chloro-9-borafluorene and ligand exchange reactions

Cyclic 1,2-diphenylenediboranes containing a doubly hydrogen-bridged structure, including 1,2-(2,2^′biphenylylene)diborane(I) and 1,2-(2,2^′biphenylylene)-1,2-diethyldiborane (II), are conveniently prepared by treating 9-chloro-9-borafluorene with NaBH₄ and Na(Et)₃BH, respectively. The reaction mechanism involves an initial Cl-H exchange to form 9-borafluorene containing a reactive 5-member ring diarylborane moiety, which subsequently engages in a facile ring expansion with the in situ formed B-H containing residue (BH₃ or HBEt₂) to result in cyclic 1,2-diphenylenediboranes compounds. The doubly hydrogen-bridged structure shows good thermal stability up to 50 °C. Upon thermal cleavage at higher temperature, all free B-H groups become very reactive involving hydroboration with α-olefin. The complexization study also reveals that this intradiborane moiety forms a 1:2 complex with a strong base, such as pyridine.     

Synthesis and structure of 9-hydroxy-1,2-dicarba-closo-dodecaborane(11)

The oxidation of 1,2-C₂B₁₀H₁₂ (1) with 100% nitric acid was studied in two solvents (CH₂C1₂ and CCl₄). Under the action of superacid (CF3SO3H), the compound 9-HO-1,2-C₂B₁₀H₁₁ (2) gives the onium cation 9-H₂O⁺-1,2-C₂B₁₀H₁₁ involved in the salt [9-H₂O⁺-1,2-C₂B₁₀H_n]-CF₃SO₃^?, as demonstrated by ^uB NMR spectroscopy. The experimental and simulated ^uB NMR spectra of the cation 9-H₂O⁺-1,2-C₂B₁₀H₁₁ are in satisfactory agreement with each other. In the presence of a base, compound 2 is transferred from an ethereal solution to an aqueous alkaline solution giving the anion 9-O^?- 1,2-C₂B₁₀H₁₁. The structure of compound 2 was confirmed by ¹H, ¹¹B, ¹¹B¹H, ¹¹B-¹¹B COSY NMR spectroscopy, IR spectroscopy, and gas chromatography mass spectrometry and was additionally established by X-ray diffraction.

     

Synthesis and Characterization of Novel Chiral (1R,2R)-1,2-Bis[5-(Aminomethylphospinic Acid)-1,3,4-Thiadiazol-2-YL]Ethane-1,2-Diols

Abstract

(1R,2R)-1,2-bis[5-(arylideneamino)-1,3,4-thiadiazol-2-yl]ethane-1,2-diol (2a–d) were synthesized by using appropriate aldehydes and (1R,2R)-1,2-bis(5-amino-1,3,4-thiadiazol-2-yl)ethane-1,2-diol (1) as a starting compound. Then, the phosphinic acid component (3a–d) were obtained from (2a–d) and hypophosporus acid. In addition, the structures of the novel chiral compounds (2a–d) and (3a–d) were confirmed by elemental analyses, IR, ¹H-NMR, ¹³C-NMR, and ³¹P-NMR spectra.

¹H NMR and ¹³C NMR spectra for 1, 2a, and 3a (Figures S1–S6) are available online in the Supplemental Materials.     

Synthesis of 1‐silacyclopent‐2‐ene derivatives using 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of di(alkyn‐1‐yl)vinylsilanes R¹(H₂C═CH)Si(C≡C―R)₂ (R¹ = Me ( 1 ), Ph ( 2 ); R = Bu (a), Ph (b), Me₂HSi (c)) at 25°C with 1 equiv. of 9‐borabicyclo[3.3.1]nonane (9‐BBN) affords 1‐silacyclopent‐2‐ene derivatives ( 3a , 3b , 3c , 4a , 4b ), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2‐hydroboration followed by intramolecular 1,1‐carboboration. Treated with a further equivalent of 9‐BBN in benzene they are converted at relatively high temperature (80–100°C) into 1‐alkenyl‐1‐silacyclopent‐2‐ene derivatives ( 5a , 5b 6a , 6b ) as a result of 1,2‐hydroboration of the Si―C≡C―R function. Protodeborylation of the 9‐BBN‐substituted 1‐silacyclopent‐2‐ene derivatives 3 , 4 , 5 , 6 , using acetic acid in excess, proceeds smoothly to give the novel 1‐silacyclopent‐2‐ene ( 7 , 8 , 9 , 10 ). The solution‐state structural assignment of all new compounds, i.e. di(alkyn‐1‐yl)vinylsilanes and 1‐silacyclopent‐2‐ene derivatives, was carried out using multinuclear magnetic resonance techniques (¹H, ¹³C, ¹¹B, ²⁹Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6‐311+G/(d,p) level of theory), and ²⁹Si NMR parameters were calculated (chemical shifts δ²⁹Si and coupling constants ⁿJ(²⁹Si,¹³C)). Copyright © 2014 John Wiley & Sons, Ltd.     

Koordinationseigenschaften von Carbaboranylchlorophosphanen: Synthese und Molekülstruktur von cis-rac-Molybdäntetracarbonyl{1,2-bis(chlorophenylphosphino)-1,2-dicarba-closo-dodecaboran(12)}

Coordination Properties of Carbaboranylchlorophosphines: Synthesis and Molecular Structure of cis-rac -Molybdenumtetracarbonyl{1,2-bis(chlorophenylphosphino)-1,2-dicarba-closo-dodecaborane(12)} Rac-1,2-bis(chlorophenylphosphino)-1,2-dicarba-closo-dodecaborane(12) ( 1 ) reacts with [Mo(CO)₄(NBD)] (NBD = norbornadiene) after several hours at 50–55 °C to yield cis-rac-[Mo(CO)₄{1,2-(PPhCl)₂C₂B₁₀H₁₀}] ( 2 ). 2 was characterised spectroscopically (¹H, ¹³C, ¹¹B and ³¹P NMR) and by crystal structure determination.     

A Reductive 1,2 Transposition of Acyclic Ketones

Earlier we noted that the hydroboration of the trimethylsilyl enol ether of an acyclic ketone results in an elimination of a trimethylsiloxyborane moiety with the subsequent formation of an olefin.^1,2 The olefin formed then undergoes hydroboration giving a monoalcohol upon oxidation. (eq 1) We wish to report here on the utility of this sequence, illustrated in eq 1, in the reductive 1,2 transposition of acyclic ketones.³     

Synthesis and structure of novel spirosilanes. Combination of 1,2‐hydroboration and 1,1‐organoboration

The reaction of tetra(alkyn‐1‐yl)silanes Si(C?C‐R¹)₄ 1 [R¹ = ^tBu ( a ), Ph ( b ), C₆H₄‐4‐Me ( c )] with 9‐borabicyclo[3.3.1]nonane (9‐BBN) in a 1:2 ratio affords the spirosilane derivatives 5a – c as a result of twofold intermolecular 1,2‐hydroboration, followed by twofold intramolecular 1,1‐organoboration. Intermediates 3a–c , in which two alkenyl‐ and two alkyn‐1‐yl groups are linked to silicon, were identified by NMR spectroscopy. The molecular structure of the spiro compound 5c was determined by X‐ray analysis, and the solution‐state structures of products and intermediates follow conclusively from the consistent NMR spectroscopic data sets (¹H, ¹¹B, ¹³C and ²⁹Si NMR). Copyright © 2008 John Wiley & Sons, Ltd.     

Syntheses and conformations of some cyclic hydroxamates. X-Ray crystal structure of 2-(p-nitrobenzoyl)tetrahydro-2H-1,2-oxazine

Alkylation of potassium p-nitrobenzohydroxamate with 1,4-dibromobutane gave 2-(p-nitrobenzoyl)tetrahydro-2H-1,2-oxazine (3). The X-ray crystal structure of 3 has been determined. The crystals are monoclinic, space group P2₁/n with a = 6.749(1), b = 7.644(1), c = 21.557(2)Å, β = 98.89(1), V = 1098.8(2)ų and Z = 4. The structure, which was refined to R = 0.039 using 1340 observed reflections, shows the oxazine and carbonyl oxygen atoms trans to each other. Alkylation of potassium benzohydroxamate with 1,3-dibromobutane gave a mixture of 3-methyl-2-benzoyloxazolidine (4) and 5-methyl-2-benzoyloxazolidine (5). The ¹H and ¹³C nmr spectra of the mixture of 4 and 5 indicates that these cyclic hydroxamates exist predominantly in the s-trans conformation.     

Thermolysis of [tris(trimethylsilyl)methyl](diphenyl)fluorosilane. Isomerization of a sila-olefin intermediate

The compound (Me₃Si)₃CSiPh₂F loses Me₃SiF under reflux or on passage through a tube at 450°C to give three products, A, B, and C, in approximately 20/20/60 ratio. Products A and B, which are solids, were shown by X-ray crystallographic analysis to be the diastereoisomeric forms of 1-dimethylsila-2-trimethylsilyl-3-[(methyl)(phenyl)sila]indane. From its mass and ¹H NMR spectra, C (a liquid) was tentatively identified as 1,3-bis(dimethylsila)-2-[(dimethyl)(phenyl)silyl]indane. All three products are isomers of the sila-olefin (Me₃Si)₂CSiPh₂, and it is suggested that the latter is first formed by loss of Me₃SiF from (MeSi)₃CSiPh₂F, and the equilibrium (Me₃Si)₂CSiPh₂ ? (Me₃Si)(Ph₂MeSi)CSiMe₂ ? (Me₃Si)(PhMe₂Si)CSiMePh ? (Me₂PhSi)₂CSiMe₂ is then rapidly established; internal cyclizations involving addition of aryl CH bonds across SiC bonds then occur to give the observed products. Consistent with this is the observation that a mixture of silicon alkoxides, thought to be (Me₃Si)₂CHSiPh₂OMe and its isomers (which would be formed by addition of methanol across the SiC bonds of the four sila-olefins) is produced when methanol is passed through the hot tube with the (Me₃Si)₃CSiPh₂F.Full structural details are given for compounds A and B. Some features of interest are: (a) the conformation of the 5-membered ring is different in the two diastereoisomers; (b) the exocyclic SiCSiMe₃ bond angles, of ca. 120° are unusually large; and (c) there is a little distortion of the fused benzene ring, which is attributed to the effect of silicon substituents on the hybridization of carbon atoms to which they are attached.     

Organoborierung von alkinylstannanen: XV. Synthese von 1,2-dihydro-1,2,5-disilaborepinen

The reaction between 1,2-diethynyl-tetramethyldisilane (1) and two equivalents of diethylaminotrimethylstannane (2) leads to 1,2-bis(trimethylstannylethynyl)-tetramethyldisilane (3). The new alkyne derivative 3 reacts, already at room temperature, with trialkylboranes, R₃B (5) (R = Me, Et), quantitatively to give 1,1,2,2-tetramethyl-3,7-bis(trimethylstannyl)-4,5,6-trialkyl-1,2-dihydro-1,2,5-disilaborepines (6). The reaction is much slower with R = Prⁱ which allows detection of intermediates by NMR spectroscopy. All products are characterized by ¹H, ¹¹B, ¹³C, ²⁹Si and ¹¹⁹Sn NMR data.     

Regioselective Rhodium-Catalyzed 1,2-Hydroboration of Pyridines and Quinolines Enabled by the Tris(8-quinolinyl)phosphite Ligand**

A Rh(I) complex [κ²(P,N)-{P(Oquin)₃}RhCl(PPh₃)] ( 1 ) bearing the P,N ligand tris(8-quinolinyl)phosphite, P(Oquin)₃, has been synthesized and structurally characterized. The molecular structure of complex 1 shows that P(Oquin)₃ acts as a bidentate P,N chelate ligand. Reactivity studies of 1 reveal that the triphenylphosphine ligand can be replaced by Pcy₃ or removed upon oxidation with concomitant coordination of a second 8-quinolyl unit of P(Oquin)₃. In addition, the Rh(III) complex [RhCl₂{OP(Oquin)₂}] ( 3 ), resulting from treating 1 with either wet CDCl₃ or, sequentially, with HCl and water, was identified by X-ray diffraction analysis. Complex 1 catalyzes the 1,2-regioselective hydroboration of pyridines and quinolines, affording N-boryl-1,2-dihydropyridines (1,2-BDHP) and N-boryl-1,2-hydroquinolines (1,2-BDHQ) in high yield (up to >95 %) with turnover numbers (TONs) of up to 130. The system tolerates a variety of substrates of different electronic and steric nature. In comparison with other transition-metal-based hydroboration catalysts, this system is efficient at a low catalyst loading without the requirement of base or other additives.     

Heterometallic cluster complexes (RhMo, RhW) containing bridging 1,2-dicarba-closo-dodecaborane-1,2-dichalocogenolato ligands

The 16-electron half-sandwich rhodium complex [Cp*Rh{E2C2(B10H10)}] [Cp* = eta5-C5Me5, E = S (1a), Se (1b)] [Cp*Rh{E2C2(B10H10)} = eta5-pentamethylcyclopentadienyl[1,2-dicarba-closo-dodecaborane(12)-dichalcogenolato]rhodium] reacted with Mo(CO)3(py)3 in the presence of BF3.Et2O in THF solution to afford the {Cp*Rh[E2C2(B10H10)]}2Mo(CO)2 (E = S (3a); Se (3b)), {Cp*Rh[S2C2(B10H10)]}{Mo(CO)2[S2C2(B10H10)]} (4). The voluminous di-tert-butyl substituted Cp half-sandwich rhodium complex [Cp'Rh{E2C2(B10H10)}] [E = S (2a), Se (2b)] [CpRh{E2C2(B10H10)} = eta5-(1,3-di(tert-butyl)cyclopentadienyl-[1,2-dicarba-closo-dodecaborane(12)-dichalcogenolato]rhodium) reacted with W(CO)3(py)3 in the presence of BF3.Et2O in THF solution to give the {Cp'Rh[S2C2(B10H10)]}{W(CO)2[S2C2(B10H10)]} (5) and {Cp'Rh[Se2C2(B10H10)]}(mu-CO)[W(CO)3] (6), respectively. The complexes have been fully characterized by IR and NMR spectroscopy as well as by elemental analyses. The X-ray crystal structures of the complexes 3-6 are reported.     

Synthesis and structural characterization of ruthenium(II) and iron(II) complexes containing 1,2-di-(2-thienyl)-ethene derived ligands as chromophores

A new family of three-legged piano stool structured organometallic compounds containing the η⁵-cyclopentadienylruthenium(II)/iron(II) fragments {M(η⁵-C₅H₅) (DPPE)}⁺, {Ru(η⁵-C₅H₅)(PPh₃)₂}⁺ and {Ru(η⁵-C₅H₅)(TMEDA)}⁺ with coordinated thiophene based chromophores, namely 5-(2-thiophen-2-yl-vinyl)-thiophene-2-carbonitrile (L1) and 5-[2-(5-Nitro-thiophen-2-yl)-vinyl]-thiophene-2-carbonitrile (L2) has been synthesized and fully characterized by ¹H, ¹³C, ³¹P NMR, IR and UV-Vis spectroscopies. Also, electrochemical studies were carried out by cyclic voltammetry and all experimental data are interpreted and compared with related compounds under the scope of NLO properties. Compounds [Ru(η⁵-C₅H₅)(DPPE)(NC(C₄H₂S)C(H)C(H)(C₄H₃S))][CF₃SO₃] (1′Ru) [Fe(η⁵-C₅H₅)(DPPE)(NC(C₄H₂S)C(H)C(H)(C₄H₃S))] [PF₆] (1Fe) and [Ru(η⁵-C₅H₅)(DPPE)(NC(C₄H₂S)C(H)C(H)(C₄H₂S)NO₂)][CF₃SO₃] (4′Ru) were also crystallographically characterized.     

Synthesis and Crystal Structure of (Z)-Ethyl 5-(phenylamino)-3-(phenylimino)-3H-1,2-dithiole-4-carboxylate

The compound (Z)-ethyl 5-(phenylamino)-3-(phenylimino)-3H-1,2-dithiole-4-carboxylate 3 has been synthesized by the reaction of ethylacetoacetate 1 and phenylisothiocyanate 2. Its structure has been established by ¹H NMR, ¹³C NMR, infrared, mass spectra, and x-ray crystallography.      

Enantiomerically Pure Cyclic trans-1,2-Diols,Diamines, and Amino Alcohols by Intramolecular Pinacol Coupling of Planar Chiral Mono-Cr(CO)3 Complexes of Biaryls

Without any formation of stereoisomers , the intramolecular pinacol cyclization of 1 —planar chiral mono-Cr(CO)₃ complexes of 1,1′-biphenyls with carbonyl functionalities at the 2- and 2′-positions—with samarium diiodide gives cyclic trans-1,2-diols 2 . Upon exposure to sunlight, the chromium-complexed diols 2 produce optically pure chromium-free trans-diols 3 . Similarly, the corresponding enantiomerically pure trans-1,2-diamines and amino alcohols are obtained from the planar chiral chromium complexes of biphenyls with diimino or keto-imino functionalities. R¹=H, OMe; R²=H, Me; R³=H, Me.     

1,3,2-Diazasiloles derived from 1,2-bis(trimethylsilylimino)acenaphthene

The reduction of 1,2-bis(trimethylsilylimino)acenaphthene (tms-BIAN, 1) with metallic lithium in toluene affords the dilithium salt (tms-BIAN)Li_2· 1,3,2-Diazasiloles (tms-BIAN)SiCl₂ (2) and (tms-BIAN)SiMe₂ (3) were prepared by the reactions of (tms-BIAN)Li₂ with SiCl₄ and Me₂SiCl₂, respectively. The reaction of (tms-BIAN)Li₂ with an excess of Me₂SiCl₂ produces (Cldms-BIAN)SiMe₂ (4), where Cldms-BIAN is 1,2-bis(chlorodimethylsilylimino)-acenaphthene. The compound (tms-BIAN)(SiCl₃)₂ (5) containing two different silyl substituents (Me₃Si and Cl₃Si) at each nitrogen atom was synthesized by the reaction of compound 1 with Cl₃SiSiCl₃. The elimination of SiCl₄ from compound 5 is accompanied by cyclization to give derivative 2. Compounds 2-5 were characterized by ¹H, ¹³C, and ²⁹Si NMR spectroscopy. The crystal structures of 2-5 were established by X-ray diffraction.     

Chiral functionalized bisphosphine ligands: Transition metal complexes of 1,2-bis(tert-Butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12)

When rac- or meso-1,2-bis(tert-butylchlorophosphino)-1,2-dicarba-closo-dodecaborane(12) (1a or 1b) is reacted with [M(CO)₄(NBD)] (M = Cr, Mo, NBD = norbornadiene), [Mo(CO)₄(EtCN)₂] or [W(CO)₆], rac-[Cr(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (2), rac- or meso-[Mo(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (3a or 3b) and rac-[W(CO)₄{1,2-(P^tBuCl)₂C₂B₁₀H₁₀}] (4) could be isolated as pure diastereomers. UV irradiation of 1 with [Cr(CO)₆] in moist THF proceeds with hydrolysis and formation of [Cr(CO)₄{1,2-(P(OH)^tBu)₂C₂B₁₀H₁₀}] (5) which contains the metal complex-stabilized phosphinous acid. Compounds 2–5 were characterized spectroscopically (¹H, ³¹P, ¹¹B, ¹³C NMR), by mass spectrometry and by X-ray structure determination.     

Hochdruckversuche—IX: Die thermische isomerisierung von 1,2-diphenyl-3-methyl-cyclobuten-(1)-cis-3,4-dicarbonsäuredimethylester und 3,4-dimethyl-1,2-diphenyl-cyclobuten-(1)-cis-3,4-dicarbonsäuredimethylester

Dimethyl-1,2-diphenyl-3-methyl-cyclobutene-(1)-cis-3,4-dicarboxylate 2 leads in a thermal reaction to an equilibrium with (E, Z)-dimethyl-3,4-diphenyl-5-methyl-muconate (4). The equilibrium is shifted to the cyclic compound by pressure. Dimethyl-3,4-diphenyl-cyclobutene-(1,2-diphenyl-cyclobutene-(1)-cis-3,4-dicarboxylate (3) isomerizes thermally to (E, Z)-dimethyl-2,5-dimethyl-3,4-diphenylmuconate (6). Both reactions are accelerated by pressure. The activation volumes ΔV₀⁺ are given for each ringopening reaction.