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.     

Synthesis and molecular structures of 1‐chloro‐1‐silacyclopent‐2‐enes. Combination of 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of alkyn‐1‐yl(chloro)(methyl)vinyl‐ and alkyn‐1‐yl(chloro)(phenyl)‐vinylsilane with 9‐borabicyclo[3.3.1]nonane (9‐BBN) afforded selectively 1‐silacyclopent‐2‐ene derivatives containing a Si? Cl function, as a result of consecutive 1,2‐hydroboration and 1,1‐organoboration. Protodeborylation with acetic acid left the Si? Cl functions in various 1‐silacyclopent‐2‐enes untouched, whereas acetic acid in the presence of dipropylamine led to conversion of the Si? Cl into the Si? OAc function. New starting materials and all products were characterized in solution by multinuclear NMR spectroscopy (¹H, ¹¹B, ¹³C and ²⁹Si NMR), and the molecular structures of two 1‐silacyclopent‐2‐ene derivatives were determined by X‐ray analysis. The gas phase geometries of 1‐silacyclopent‐2‐enes were optimized by DFT calculations [B3LYP/6‐311 + G(d,p) level of theory], found to be in reasonable agreement with the results of the crystal structure determination, and NMR parameters were calculated at the same level of theory. Copyright © 2009 John Wiley & Sons, Ltd.     

1‐Silacyclopent‐2‐enes and 1‐silacyclohex‐2‐enes bearing functionally substituted silyl groups in 2‐positions. Novel electron‐deficient Si?H?B bridges

The reactions of alkyn‐1‐yl(vinyl)silanes R₂Si[C?C‐Si(H)Me₂]CH?CH₂ [R = Me (1a), Ph (1b)], Me₂Si[C?C‐Si(Br)Me₂]CH?CH₂ (2a), and of alkyn‐1‐yl(allyl)silanes R₂Si[C?C‐Si(H)Me₂]CH₂CH?CH₂ (R = Me (3a), R = Ph (3b)] with 9‐borabicyclo[3.3.1]nonane in a 1:1 ratio afford in high yield the 1‐silacyclopent‐2‐ene derivatives 4a, b and 5a, and the 1‐silacyclohex‐2‐ene derivatives 6a, b, respectively, all of which bear a functionally substituted silyl group in 2‐position and the boryl group in 3‐position. This is the result of selective intermolecular 1,2‐hydroboration of the vinyl or allyl group, followed by intramolecular 1,1‐organoboration of the alkynyl group. In the cases of 4a, b, potential electron‐deficient Si? H? B bridges are absent or extremely weak, whereas in 6a,b the existence of Si? H? B bridges is evident from the NMR spectroscopic data (¹H, ¹¹B, ¹³C and ²⁹Si NMR). The molecular structure of 4b was determined by X‐ray analysis. Copyright © 2005 John Wiley & Sons, Ltd.     

1,1‐Ethylboration of alkyn‐1‐yl‐chloro(methyl)silanes: alkenes with chloro(methyl)silyl and diethylboryl groups in cis positions

The 1,1‐ethylboration of alkyn‐1‐yl‐chloro(methyl)silanes, Me₂Si(Cl)? C?C? R ( 1 ) and Me(H)Si(Cl)? C?C? R ( 2 ) [R = Bu ( 2a ), CH₂NMe₂ ( 2b )] requires harsh reaction conditions (up to 20 days in boiling triethylborane), and leads to alkenes in which the boryl and silyl groups occupy cis ((E)‐isomers: 3a , 3b , 5a , 5b ) or trans positions ((Z)‐isomers in smaller quantities: 4b and 6b ). The alkenes are destabilized in the presence of SiH(Cl) and CH₂NMe₂ units ( 5b , 6b ). NMR data indicate hyper‐coordinated silicon by intramolecular N? Si coordination in 3b and 5b , by which, at the same time, weak Si? Cl? B bridges are favoured. Copyright © 2005 John Wiley & Sons, Ltd.     

Synthesis and molecular structures of 1‐boracyclopent‐2‐enes

The reaction of 1‐silyl‐1‐borylalkenes with alkyn‐1‐yltin compounds affords borol‐2‐enes, organometallic‐substituted allenes, mixtures thereof or even more complex mixtures with buta‐1,3‐dienes, depending on the third substituent at the C?C bond (Bu or Ph), on the number of Si? Cl functions (two or three) and the nature of the alkyn‐1‐yltin compound. Six new borol‐2‐enes were isolated in pure state, and two of them were characterized by X‐ray structural analysis. The solution‐state structures of all major products were clearly established by multinuclear magnetic resonance methods (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2009 John Wiley & Sons, Ltd.     

Boryl‐substituted 1‐silacyclobutenes. Formation and molecular structure

The 1,2‐hydroboration of the chloro(hexyn‐1‐yl)‐ ( 1a ) and chloro(phenylethyn‐1‐yl)diphenylsilanes ( 1b ) with 9‐borabicyclo[3.3.1]nonane afforded selectively the alkenylsilanes 2a, b , in which the boryl and the silyl groups are linked to the same olefinic carbon atom. In case of 2a , treatment with phenylethynyl lithium gave a mixture of the alkyn‐1‐ylborate 3a and the alkenyl(phenylethynyl)diphenylsilanes 4a . In the case of 2b , only the alkyn‐1‐ylsilane 4b was identified as an intermediate. Both 4a, b slowly rearranged by intramolecular 1,1‐vinylboration into the silacyclobutenes 5a, b . The intermediates were characterized by ¹H, ¹¹B, ¹³C and ²⁹Si NMR spectroscopy in solution, and the molecular structure of the 1‐silacyclobutene 5a was determined by X‐ray analysis. The gas phase geometries of model molecules corresponding to 5a were optimized by MO calculations using DFT methods [B3LYP/6‐311 + G(d,p) level of theory], found to be in reasonable agreement with the results of the crystal structure determination, and NMR parameters were calculated at the same level of theory. Copyright © 2006 John Wiley & Sons, Ltd.     

Metallacyclopentadienes and related heterocycles via 1,1‐organoboration of alkyn‐1‐ylmetal compounds

Metallacyclopentadienes (metalloles) containing M = Si, Ge, Sn, Pb, Ti, Pt can be prepared by 1,1‐organoboration of alkyn‐1‐ylmetal compounds L_nM CC R¹(R¹ = H, alkyl, aryl, silyl, etc; L depends on M, and can be hydrogen, alkyl, aryl, Cl, Br, amino groups, a chelating diphosphane, and one or more L can be again alkynyl groups). These reactions proceed via activation of the M C bond(s) by an electron‐deficient triorganoborane BR₃ (R = alkyl, aryl; non‐cyclic, monocyclic, bicyclic, and tricyclic boranes), at first intermolecular and then intramolecular. In the course of these reactions, the M C bonds are cleaved, zwitterionic alkynylborate‐like intermediates are formed, in which the metal‐containing fragments are coordinated side‐on to the CC bonds. In most cases, the 1,1‐organoboration reactions tolerate various functional groups at the alkyne as well as at the metal. The characterization of intermediates and final products by X‐ray structural analysis and by multinuclear magnetic resonance spectroscopy (NMR) is documented and described. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:188–208, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20222     

Aminoethynyl‐silanes, ‐germanes and ‐stannanes: novel organometallic‐substituted enamines via 1,1‐organoboration

The reactions of diethylaminoethynyl(trimethyl)silane (1), bis(diethylaminoethynyl)methylsilane (2), diethylaminoethynyl(trimethyl)germane (3), dimethylaminoethynyl(triethyl)germane (4), diethylaminoethynyl(trimethyl)stannane (5) and methyl(phenyl)aminoethynyl(trimethyl)stannane (6) with trialkylboranes [BEt₃ (7b), BPr₃ (7c), BⁱPr₃ (7d) and 9‐alkyl‐9‐borabicyclo[3.3.1]nonanes 9‐Me‐9‐BBN (8a) and 9‐Et‐9‐BBN (8b)] were studied. The alkynes 1 and 2 did not react even with boiling BEt₃, whereas the reactions of 3–6 afforded mainly novel enamines [(E)‐1‐amino‐1‐trialkylgermyl‐2‐dialkylboryl‐alkenes (9, 10), (E)‐1‐diethylamino‐1‐trimethylstannyl‐2‐dialkylboryl‐alkenes (11, 12), (E)‐1‐methyl(phenyl)amino‐1‐trimethylstannyl‐2‐dialkylboryl‐alkenes (13, 14)]. This particular stereochemistry is unusual for products from 1,1‐organoboration reactions, indicating a special influence of the amino group. The starting materials and products were characterized by multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, ¹⁵N, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd.     

Structure and Bonding Nature of the Strained Lewis Acid 3‐Methyl‐1‐boraadamantane: A Case Study Employing a New Data‐Analysis Procedure in Gas Electron Diffraction

Base‐free 3‐methyl‐1‐boraadamantane was synthesized by starting from its known THF adduct, transforming it to a butylate‐complex with n‐butyllithium, cleaving the cage with acetyl chloride to give 3‐n‐butyl‐5‐methyl‐7‐methylene‐3‐borabicyclo[3.3.1]nonane and closing the cage again by reacting the latter with dicyclohexylborane. The identity of 3‐methyl‐1‐boraadamantane was proven by ¹H, ¹¹B and ¹³C NMR spectroscopy and elemental analysis. The experimental equilibrium structure of the free 3‐methyl‐1‐boraadamantane molecules has been determined at 100 °C by using gas‐phase electron diffraction. For this structure determination, an improved method for data analysis has been introduced and tested: the structural refinement versus gas‐phase electron diffraction data (in terms of Cartesian coordinates) with a set of quantum‐chemically derived regularization constraints for the complete structure under optimization of a regularization constant, which maximizes the contribution of experimental data while retaining a stable refinement. The detailed analysis of parameter errors shows that the new approach allows obtaining more reliable results. The most important structural parameters are: r_e(B‐C)_av=1.556(5) Å, ${\angle }$ _e(C‐B‐C)_av=116.5(2)°. The configuration of the boron atom is pyramidal with ${\sum \angle }$ (C‐B‐C)=349.4(4)°. The nature of bonding was analyzed further by applying the natural bond orbital (NBO) and atoms in molecules (AIM) approaches. The experimentally observed shortening of the B? C bonds and elongation of the adjacent C? C bonds can be explained by the σ(C‐C)→p(B) hyperconjugation model. Both NBO and AIM analyses predict that the B? C bonds are significantly bent in the direction out of the cage.     

1,1‐Organoboration of bis(trimethylstannyl)ethyne with trimethylsilyl‐ and dimethylsilyl‐dialkylboryl‐substituted alkenes: organometallic‐substituted allenes

The reactions of bis(trimethylstannyl)ethyne, Me₃Sn–C?C–SnMe₃ ( 4 ), with trimethylsilyl‐ or dimethylsilyl‐dialkylboryl‐substituted alkenes 1 – 3 afford organometallic‐substituted allenes 5 , 6 and 8 , 9 in high yield. In the case of (E)‐2‐trimethylsilyl‐3‐diethylboryl‐2‐pentene ( 1) , a butadiene derivative 7 could be detected as an intermediate prior to rearrangement into the allene. All reactions were monitored by ²⁹Si and ¹¹⁹Sn NMR, and the products were characterized by an extensive NMR data set (¹H, ¹¹B, ¹³C, ²⁹Si, ¹¹⁹Sn NMR). Copyright © 2003 John Wiley & Sons, Ltd.     

An Unexpected and Green Synthetic Protocol for Ethyl 1‐Aroyl/Aroylmethyl‐5‐methyl‐3‐methylthiopyrazole‐4‐carboxylates: High Regioselectivity in Alkylation and Acylation Reactions between N‐1 and N‐2 of a Pyrazole Ring

Two series, totaling twelve, of new compounds, ethyl 1‐aroyl/(aroylmethyl)‐5‐methyl‐3‐methylthiopyrazole‐4‐carboxylates ( 5 / 6 ), have been synthesized via highly regioselectively acylation and alkylation reactions of ethyl 3‐methyl‐5‐methylthio‐1 H‐pyrazole‐4‐carboxylate ( 2a ) with aroyl chloride ( 3 ) and eco‐friendly reagents alpha‐tosyloxysubstituted acetophenones ( 4 ), respectively, and a green protocol has been developed. The acylation reactions were carried out under ultrasound irradiation, and the alkylation reactions were under microwave irradiation and ultrasound irradiation, respectively. Conventional reaction conditions, as well as the use of alpha‐bromosubstituted acetophenone ( 4 ′) have also been applied in the synthesis of some randomly selected compounds in both series and have generated identical compounds correspondingly. Unexpected structures of compounds were unambiguously determined by X‐ray crystallographic analysis.     

The Structure of 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine in the Solid State and in Solution; Unprecedented Cocrystallization of Four Stereoisomers

The solid and solution structures of a new optically active aminopyridine compound, 2‐[(1S)‐(+)‐10‐camphorsulfonamino]‐6‐aminopyridine [(S)‐csaap], 1 , are reported. Crystal data: space group P2₁, a = 8.9729 (5), b = 10.9447 (6), c = 36.693 (2) Å, β = 96.435 (1)°, V = 3580.8 (3) ų, Z = 8, R₁ = 0.0673 and wR₂ = 0.1600 with I > 2σ(I). This chiral compound shows an unprecedented cocrystallization of four stereoisomers, which are characterized by X‐ray crystallography and NMR spectroscopy.     

Experimental and quantum chemical calculational studies on N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐hydrazine

The title molecule, N‐[4‐(3‐Methyl‐3‐phenyl‐cyclobutyl)‐thiazol‐2‐yl]‐N′‐pyridin‐3ylmethylene‐ hydrazine (C₂₀ H₂₀ N₄ S₁), was characterized by ¹H‐NMR, ¹³C‐NMR, IR, UV‐visible, and X‐ray determination. In addition to the molecular geometry from X‐ray experiment, the molecular geometry, vibrational frequencies and gauge including atomic orbital ¹H‐ and ¹³C‐NMR chemical shift values of the title compound in the ground state have been calculated using the Hartree‐Fock and density functional method (B3LYP) with 6‐31G(d, p) basis set. The calculated results show that optimized geometries can well reproduce the crystal structural parameters. By using time‐dependent density functional theory method, electronic absorption spectrum of the title compound has been predicted. © 2011 Wiley Periodicals, Inc.     

Energetic Materials Based on the 5‐Azido‐3‐nitro‐1, 2,4‐tri­azolate Anion

This study presents the preparation of 5‐azido‐3‐nitro‐1H‐1, 2,4‐triazole ( 1 ) in both good yield and high purity, starting from commercially available chemicals in a three step synthesis. Furthermore, several metal and nitrogen‐rich salts with sodium ( 3 ), potassium ( 4 ), cesium ( 5 ), silver ( 6 ), lead ( 7 ), ammonium ( 8 ), guanidinium ( 9 ), and aminoguanidinium ( 10 ) were prepared by simple acid‐base reactions. All compounds were well characterized by various means, including vibrational (IR, Raman) and multinuclear (¹H, ¹³C, ¹⁴N, ¹⁵N) NMR spectroscopy, mass spectrometry, and DSC. Additionally the structure of 7 was determined by single‐crystal X‐ray diffraction. The sensitivities towards various outer stimuli (impact, friction, electrostatic discharge) were determined according to BAM standards. The metal salts were tested as potential primary explosives utilizing various preliminary tests.     

Ionic Liquids as Unique Solvents in One‐Pot Synthesis of 4‐(N,2,2,2‐Tetranitroethylamino)‐3‐R‐Furazans

An efficient two‐step one‐pot protocol for the synthesis of N‐nitrated trinitroethylamino furazans in an ionic liquid has been developed involving the condensation of aminofurazans with trinitroethanol and the N‐nitration of an intermediate Mannich base. Trinitroethylnitramino derivatives have been synthesized and characterized by multinuclear NMR spectroscopy and X‐ray crystallography. A role of the N,2,2,2‐tetranitroethylamino group for stabilization of the high‐density crystal‐packing motif is described. The performance calculations gave detonation pressures and velocities for the furazan derivatives in a range of about 31–36 GPa and 8330–8745 ms^?1, respectively, which makes them competitive energetic materials. Furthermore, due to the positive oxygen balance, the compounds could be potential oxidizers for energetic formulations.     

1,3‐Bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophanes

The 2‐tert‐butyl, 2‐phenoxy, and 2‐diethylamino derivatives of 1,3‐bis(trimethylsilyl)‐1,3,2‐diazaphospha‐[3]ferrocenophane were prepared, and the molecular structure of the latter was determined by X‐ray diffraction. The phosphines could be oxidized by their slow reactions with sulfur or selenium, and the molecular structures of three sulfides and one selenide were determined. In contrast, the synthesis of oxides was less straightforward. All new compounds were characterized in solution by multinuclear magnetic resonance methods (1D and 2D ¹H, ¹³C, ¹⁵N, ²⁹Si, ³¹P, and ⁷⁷Se NMR spectroscopy).     

A Study of 5‐(1,2,4‐Triazol‐C‐yl)tetrazol‐1‐ols: Combining the Benefits of Different Heterocycles for the Design of Energetic Materials

The synthesis and full structural and spectroscopic characterization of three 5‐(1,2,4‐triazol‐C‐yl)tetrazol‐1‐ol compounds with selected energetic moieties including nitrimino ( 5 ), nitro ( 6 ) and azido ( 7 ) groups are reported. The influence of those energetic moieties as well as the C? C connection of a tetrazol‐1‐ol and a 1,2,4‐triazole on structural and energetic properties has been investigated. All compounds were well characterized by various means, including IR and multinuclear NMR spectroscopy, mass spectrometry, and DSC. The molecular structures of 5 – 8 were determined in the solid state by single‐crystal X‐ray diffraction. The standard heats of formation were calculated on the CBS‐4M level of theory utilizing the atomization energy method, revealing highly positive values for all compounds. The detonation parameters were calculated with the EXPLO5 program and compared to the common secondary explosive RDX. Additionally, sensitivities towards impact, friction and electrostatic discharge were determined.     

Reaction of alkyn-1-yl(diorganyl)silanes with 1-boraadamantane: Si-H-B bridges confirmed by the molecular structure in the solid state and in solution

1-Boraadamantane 1 was treated with alkyn-1-ylsilanes 2 containing one or two Si[bond]H functions. Under mild conditions, the reaction gave 4-methylene-3-borahomoadamantane derivatives 4 quantitatively and selectively by 1,1-organoboration. An electron deficient Si-H-B bridge was present in the product. The analogous reaction of 1 with an alkyn-1-yl-disilane 3 gave the corresponding alkene derivative 5, however, without the Si-H-B bridge. Evidence for the Si-H-B bridge in 4 was given by IR data, an extensive set of NMR spectroscopical data ((1)H, (11)B, (13)C, (29)Si NMR) including various unusual isotope effects on chemical shifts and coupling constants, as well as from the molecular structure of one example, 4 e, in the solid state. The precursor of 4 e, alkyne 2 e, Ph(2)Si(H)C[triple bond]CSi(H)Ph(2), was also studied by X-ray analysis.     

Poly(9‐undecyl‐9‐methyl‐fluorene) and poly(9‐pentadecyl‐9‐methyl‐fluorene): Synthesis,solution structure,and effect of side chain asymmetry on aggregation behavior

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d₈ together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837     

1,3‐Dihydro‐1‐hydroxy‐3‐morpholin‐4‐yl‐2,1‐benzoxaborole: product of the reaction of o‐formylphenylboronic acid with morpholine

o‐Formylphenylboronic acid reacts with morpholine to form 1,3‐dihydro‐1‐hydroxy‐3‐morpholin‐4‐yl‐2,1‐benzoxaborole. The typical hydrogen‐bonded dimer motif with a planar benzoxaborole fragment has been obtained in the solid state. Copyright © 2005 John Wiley & Sons, Ltd.