Gel formation in cationic polymerization of divinyl ethers. II. 2,2-Bis{4-[(2-vinyloxy)ethoxy]phenyl}propane

Cationic polymerization of 2,2-bis{4-[(2-vinyloxy)ethoxy]phenyl}propane [CH₂CH O CH₂CH₂O C₆H₄ C(CH₃)₂ C₆H₄ OCH₂CH₂ O CHCH₂; 2], a divinyl ether with oxyethylene units adjacent to the polymerizable vinyl ether groups and a bulky central spacer, was investigated in CH₂Cl₂ at 0°C with the diphenyl phosphate [(C₆H₅O)₂P(O)OH]/zinc chloride (ZnCl₂) initiating system. The polymerization proceeded quantitatively and gave soluble polymers up to 85% monomer conversion. In the same fashion as the polymerization of 1,4-bis[2-vinyloxy(ethoxy)]benzene (CH₂CH O CH₂CH₂O C₆H₄ OCH₂CH₂ O CHCH₂; 1) that we already studied, the content of the unreacted pendant vinyl ether groups of the produced soluble polymers decreased with monomer conversion, and almost all the pendant vinyl ether groups were consumed in the soluble products prior to gelation. Alternatively, endo-type double bonds were gradually formed in the polymer main chains by chain transfer reactions and other side reactions as the polymerization proceeded. The polymerization behavior of isobutyl vinyl ether (3), a monofunctional vinyl ether, under the same conditions, showed that the endo-type olefins in the polymer backbones are of no polymerization ability with the growing active species involved in the present polymerization systems. These results indicate that the intermolecular crosslinking reactions occurred primarily by the pendant vinyl ether groups, and the final stage of crosslinking process leading to gelation also may occur by the small amount of the residual pendant vinyl ether groups (supposedly less than 2%). The formation of the soluble polymers that almost lack the unreacted pendant vinyl ether groups is most likely due to the frequent occurrence of intramolecular crosslinking reactions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1931–1941, 1999     

Thermotropic liquid‐crystalline poly(oxadiazole)s with poly(methylene) spacers: Preparation and extraordinary odd–even effect

A novel synthetic procedure for the preparation of poly(oxadiazole)s was developed with nucleophilic substitution of α,ω-alkanediols with oxadiazole-activated bisfluoride. Seven poly(oxadiazole)s were successfully prepared by the solution polymerization of 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and various α,ω-alkanediols [HO (CH₂)_n OH, n = 5–10 or 12] in diphenyl sulfone at temperature greater than 230 °C with K₂CO₃ as a catalyst. The reduced viscosities of the poly(oxadiazole)s were 0.14–0.51 dL/g, and the decomposition temperatures were greater than 350 °C and decreased from 436 to 379 °C with increasing spacer length (n). Corresponding model compounds, consisting of two terminal mesogenic 2,5-bisphenyl-1,3,4-oxadiazole units and central poly(methylene) spacers, were also prepared for comparison. Both the polymers and model compounds exhibited an extraordinary odd–even effect: odd ones showed higher transition temperatures (melting and clearing temperatures). With differential scanning calorimetry, polarized optical microscopy (POM), and X-ray diffraction, we found that the nematic mesophase was the only texture in the melts except for the polymers with longer methylene units (n = 9), in which smectic mesophases were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 293–301, 2002     

Heats of formation and thermal stability of substituted 1,1′-Azobis(tetrazole) compounds with an extended nitrogen chain

The molecular structures of 1,1′-Azobis(tetrazole) (N₁₀) and monosubstituted compounds involving  F,  CH₃,  CN,  NH₂,  OH,  OCH₃,  N₃,  NF₂,  NO₂, and  CH₂NO₂ groups are investigated using density functional theory. The heats of formation of these compounds are investigated using ab initio composite methods. Intrinsic reaction coordinate calculations are performed to determine the energies along the decomposition pathways. The optimized geometries of the N₁₀ compounds indicate planar configurations consisting of aromatic nitrogen–nitrogen and carbon–nitrogen bonds. The stability and energy content of the substituted compounds are highly correlated with the nature of the substituents. Electron-donating groups reduce the heats of formation but increase the exothermicity of the decomposition. The decomposition of the N₁₀ compounds is classified into two general pathways: (1) a scheme involving straight-up decomposition and (2) a scheme involving functional rearrangement. Compounds undergoing decomposition pathway (1) are more exothermic with lower rate-determining activation barriers than those undergoing the latter pathway (2).     

New insight into the substituent effects on the hydrolytic deamination of saturated and unsaturated cytosine

Ab initio calculations were carried out to understand the effect of electron donating groups (EDG) and electron withdrawing groups (EWG) at the C5 position of cytosine (Cyt) and saturated cytosine (H₂Cyt) of the deamination reaction. Geometries of the reactants, transition states, intermediates, and products were fully optimized at the B3LYP/6-31G(d,p) level in the gas phase as this level of theory has been found to agree very well with G3 theories. Activation energies, enthalpies, and Gibbs energies of activation along with the thermodynamic properties (ΔE, ΔH, and ΔG) of each reaction were calculated. A plot of the Gibbs energies of activation (ΔG^‡) for C5 substituted Cyt and H₂Cyt against the Hammett σ-constants reveal a good linear relationship. In general, both EDG and EWG substituents at the C5 position in Cyt results in higher ΔG^‡ and lower σ values compared to those of H₂Cyt deamination reactions. C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) increase ΔG^‡ values for Cyt, while the same substituents decrease ΔG^‡ values for H₂Cyt which is likely due to steric effects. However, the Hammett σ-constants were found to decrease at the C5 position of cytosine (Cyt) and saturated cytosine (H2Cyt) on the deamination reaction. Both ΔG^‡ and σ values decrease for the substituents Cl and Br in the Cyt reaction, while ΔG^‡ values increase and σ decrease in the H₂Cyt reaction. This may be due to high polarizability of bromine which results in a greater stabilization of the transition state in the case of bromine compared to chlorine. Regardless of the substituent at C5, the positive charge on C4 is greater in the TS compared to the reactant complex for both the Cyt and H₂Cyt. Moreover, as the charges on C4 in the TS increase compared to reactant, ΔG^‡ also increase for the C5 alkyl substituents ( H,  CH₃,  CH₂CH₃,  CH₂CH₂CH₃) in Cyt, while ΔG^‡ decrease in H₂Cyt. In addition, analysis of the frontier MO energies for the transition state structures shows that there is a correlation between the energy of the HOMO–LUMO gap and activation energies.     

Quenching of metal‐catalyzed living radical polymerization with silyl enol ethers

Various silyl enol ethers were employed as quenchers for the living radical polymerization of methyl methacrylate with the R Cl/RuCl₂(PPh₃)₃/Al(Oi–Pr)₃ initiating system. The most effective quencher was a silyl enol ether with an electron‐donating phenyl group conjugated with its double bond [CH₂C(OSiMe₃)(4‐MeOPh) ( 2a )] that afforded a halogen‐free polymer with a ketone terminal at a high end functionality [F̄_n ∼ 1]. Such silyl compounds reacted with the growing radical generated from the dormant chloride terminal and the ruthenium complex to give the ketone terminal via the release of the silyl group along with the chlorine that originated from the dormant terminal. In contrast, less conjugated silyl enol ethers such as CH₂C(OSiMe₃)Me were less effective in quenching the polymerization. The reactivity of the silyl compounds to the poly(methyl methacrylate) radical can be explained by the reactivity of their double bonds, namely, the monomer reactivity ratios of their model vinyl monomers without the silyloxyl groups. The lifetime of the living polymer terminal was also estimated by the quenching reaction mediated with 2a . © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4735–4748, 2000     

Study on thermal degradation mechanisms of comb polyacrylates containing long fluorocarbon side chains by TG/FTIR

Thermal degradation of two series of polyacrylates containing long fluorocarbon chains [abbr.: PF_nA {HCF₂(CF₂)_n−1  CH₂ O C(O) , n = 4, 6, 8, 10} and abbr.: PFF_nEA {CF₃(CF₂)_n−1  CH₂CH₂ O C(O) , n = 6, 8, 10}] was investigated by TG /FTIR. Thermal degradation behavior of polymers changed depending on the type of tie groups, which link the fluorocarbon chains to the main chain, and also on the length of fluorocarbon chains. It was clarified that the apparent activation energies (ΔE_a ) of PF_nA series obtained by Ozawa's method varied in the order of PF₄A > PF₆A > PF₈A > PF₁₀A, while those of PFF_nEA series having tie group of  CH₂ CH₂ O C(O) were almost constant. The results for PF_nA series (tie group:  CH₂ O C(O) ) are attributable to the shield effect of long fluorocarbon chains on the back‐biting reaction in the thermal degradation of comb polymers rather than the change of C C bond dissociation energy in the main chain. It was found that TG curves of PFF_nEA series were shifted to the lower temperature region than those of PF_nA. This result can be attributable to the scission of side groups followed by the evaporation of fluorocarbon compounds and carbon dioxide. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2794–2803, 2000     

Synthesis of hybrid fluorinated silicones. I. Influence of the spacer between the silicon atom and the fluorinated chain in the preparation and the thermal properties of hybrid homopolymers

The synthesis of fluorinated hybrid silicones prepared in three steps from H₂C CH—C₆F₁₂ CH CH₂(I) and H₂C CHCH₂—C₆F₁₂—CH₂CH CH₂(II) is presented. First, both hydrosilylations of chlorodimethylsilane with these nonconjugated dienes were carried out in the presence of the Speier's catalyst leading to the expected bis-chlorosilane in excellent yield from (II) but giving a rearranged by-product from (I). However, a similar reaction from (I) initiated by a peroxide produced the expected bis-chlorosilane selectively. Second, these chlorosilanes were quantitatively hydrolyzed into the corresponding α,ω-bis silanols, whatever the spacer between the fluorinated group and the silicon atom. Finally, the polycondensations of these bis silanols were performed in the presence of an amine/acid adduct catalyst. Interestingly, the dihydroxysilane produced from (I) reacts much quicker than the other one. Moreover, thermal properties (T_g, T_dec) were investigated and compared to those of commercially available fluorosilicones or mentioned in the literature and show improvement of the behavior of these fluorosilicones at low and high temperatures. © 1996 John Wiley & Sons, Inc.     

Identification of decomposition reactions for HMDSO organosilicon using quantum chemical calculations

Hexamethyldisiloxane [HMDSO, (CH₃)₃-SiOSi-(CH₃)₃] is an important precursor for SiO₂ formation during flame-based silica material synthesis. As a result, HMDSO reactions in flame have been widely investigated experimentally, and many results have indicated that HMDSO decomposition reactions occur very early in this process. In this paper, quantum chemical calculations are performed to identify the initial decomposition of HMDSO and its subsequent reactions using the density functional theory at the level of B3LYP/6-311+G (d, p). Four reaction pathways—(a) Si O bond dissociation of HMDSO, (b) Si C bond dissociation of HMDSO, (c) dissociation and recombination of Si O and Si C bonds, and (d) elimination of a methane molecule from HMDSO—have been examined and identified. From the results, it is found that the barrier of 84.38 kcal/mol and Si O bond dissociation energy of 21.55 kcal/mol are required for the initial decomposition reaction of HMDSO in the first pathway, but the highest free energy barrier (100.69 kcal/mol) is found in the third reaction pathway. By comparing the free energy barriers and reaction rate constants, it is concluded that the most possible initial decomposition reaction of HMDSO is to eliminate the CH₃ radical by Si C bond dissociation.     

Synthesis and liquid crystalline properties of substituted 2,5‐diaryl 1,3,4‐oxadiazole derivatives without flexible chains

A series of new compounds based on aromatically 2,5‐disubstituted 1,3,4‐oxadiazoles without flexible chains, formulated as p‐R–C₆H₄–(OC₂N₂)–(p‐C₆H₄)₂–R′ with (i) R = CH₃O, R′ = CH₃O, CH₃S, F, H (Ia–Id), (ii) R = CH₃S, R′ = CH₃O, CH₃S, F, H (IIa–IId) and (iii) R = F, R′ = CH₃O, CH₃S, F, H (IIIa–IIId) (p‐C₆H₄ and OC₂N₂ represent a p‐phenylene spacer and a 1,3,4‐oxadiazole ring, respectively), were synthesised and characterised by ¹H and ¹³C NMR, MS and HRMS techniques. Mesomorphic properties were investigated using differential scanning calorimetry and polarizing optical microscopy. All of the target compounds (except Id, IId, IIIc and IIId) exhibited an enantiotropic nematic mesophase with high melting temperatures. The liquid crystalline properties of these compounds were influenced greatly by polarity, steric factors and positions of the terminal groups. The effect of the terminal groups on the liquid crystal properties is discussed.     

Nematic conformation of oxyethylene spacers involved in main-chain liquid crystals

²HNMR measurements were performed on main-chain dimer and polymer liquid crystals (LC) having oxyethylene (OE) spacers -(OCH₂CH₂)_xO-(x=2, 3). The orientational as well as conformational characteristics of these molecules have been investigated in bulk and in a nematic solution. The OE spacer was found to take spatial arrangements characteristics of the nematic phase. The nematic conformation of the spacer remains nearly invariant over a wide range of temperature and concentration. In these analyses, the ratio of the deuterium quadrupolar splittings Δν/Δν^R (Δν: spacer and Δν^R: mesogenic unit) provided an important information regarding the spatial configuration of molecules in the LC state. The results obtained in this study are consistent with our previous conclusion drawn on a series of main-chain LC oligomers and polymers comprising n-alkane spacers -O(CH₂)_nO- (n=9, 10).     

Rearrangements of (chloromethyl)organylsilanes induced by Lewis acids or by Lewis bases: Regioselective methylenation of allylic systems

In order to study the scope and mechanisms of the migration of organyl groups from silicon to its adjacent methylene carbon, a series of derivatives of the type R SiMe₂ CH₂ Cl were synthesized, where R is vinyl, benzyl, methallyl, phenylethynyl, aryloxy, and N-methylanilino. Attempts were then undertaken to induce such Si → C shifts by either the Lewis acid, methylaluminum dichloride, or the Lewis base, potassium fluoride. Under Lewis acidic conditions, only the benzyl and methylallyl groups could be induced to migrate; clearly, in the case of benzyl (and probably in the case of methallyl), migration was accompanied by allylic rearrangement to produce the o-tolyl group. Under the agency of KF, all the groups investigated underwent rearrangement to produce F SiMe₂ CH₂ R. By a crossover experiment, it was shown that, when R = aryloxy, the rearrangement occurs intermolecularly. Experimental evidence indicates that all KF-induced migrations are probably intermolecular and all MeAlCl₂-induced migrations considered here are intramolecular. The advantages for organosilicon synthesis of utilizing so-called “relay substitution reactions” with the Cl SiR₂ CH₂ Cl system are discussed: With unsymmetrical allylic systems, regioselective methylenation now becomes possible, simply by inducing the Si → C rearrangement by MeAlCl₂ or by KF.     

Electron transport membrane: Preparation of polypeptide membrane with spacers between the polymer matrix and viologen moiety and their application to an electron transfer reaction

Polypeptide membranes with several lengths of spacers [? (CH₂)_n? ; n = 3, 6, 12] between the polymer matrix and viologen moiety as a functional group were prepared. Reduction of K₃Fe(CN)₆ with Na₂S₂O₄ across the obtained membrane in aqueous media were carried out and reduction rate of K₃Fe(CN)₆ across the membrane of n = 6 was faster than that of n = 3. However, the reduction of the membrane (n = 12) did not proceed chemically and electrochemically at all.     

Crosslinked liquid crystal polymers from liquid crystal monomers: Synthesis and mechanical properties

Difunctional acrylates and methacrylate monomers have been made which are high order smectic liquid crystal (or crystalline) at room temperature. This report discusses materials with the following structure: F–S–M–S–F, where F is a functional group, acrylate or methacrylate (A or M); S is a spacer (CH₂)_n(n), and M is a mesogen—in this case 4,4′-dioxybiphenyl (B). They are codified as BnA or BnM where n is the number of methylenes in the spacer. High conversion with high T_g can be obtained when polymerizing in the smectic state because the reactive end groups are concentrated in a small volume and can react well with little or no diffusion. B2A, B3A, B6A, B11A, and B3M were polymerized in the smectic state and compared to polymers made at temperatures where the monomers were isotropic. High conversion was obtained below final T_g—even then, probably because the polymers were ordered. All the polymers were studied by WAXD and dynamic mechanical spectroscopy. Solid-state NMR on B3A showed that there was very high conversion of the double bonds at all temperatures. B3A photopolymerized in the smectic state (60–76°C) produced a crystalline polymer with T_g = 185°C (1 Hz). When photopolymerized at 85°C, above the isotropization temperature (T_i), a poorly organized polymer was obtained with a T_g of 155°C (1 Hz). Monomers with an odd number of methylene groups as spacers were crystalline after polymerization. With an even number of methylene groups, they lost most of their crystallinity on polymerization below T_i, but retained a low order smectic structure. Similar structures were obtained with all the monomers when they were polymerized above T_i. There was little effect of polymerization temperature on T_g when the spacers had an even number of methylene groups. © 1993 John Wiley & Sons, Inc.     

Multiple‐Stimulus‐Responsive Supramolecular Gels and Regulation of Chiral Twists: The Effect of Spacer Length

A new class of homologous gelators, LG₁₂‐(CH₂)_n‐BSA, composed of bipyridinyl groups, L ‐glutamic moieties having double dodecyl chains, and linked alkyl spacers with different lengths were synthesized. It was found that these gelators could immobilize medium‐polarity solvents readily and the behaviors of these gels showed a dependence on the spacer length. Of all the gels, the LG₁₂‐(CH₂)₁₁‐BSA gels exhibited self‐healing property and multiple‐stimulus responsibility, such as heating, shaking, and sonication. The investigation of CD spectra indicated that the supramolecular chirality, which was attributed to the chiral transfer from the chiral center to the assemblies, was also closely related to the length of methylene spacers. The longer the alkyl spacers, the weaker the transmitted supramolecular chirality. Only LG₁₂‐(CH₂)₁‐BSA gelators, which had the shortest spacers, formed right‐handed nanoscale chiral twists owing to crowded hydrogen bonding interactions. Moreover, the high‐polarity solvent DMF was found to be able to regulate the chiral twist as well as its pitch length readily.     

Preparation of poly(alkylenebenzimidazole) by ruthenium complex catalyzed polycondensation of 3,3′‐diaminobenzidine with α,ω‐diols

The reactions of 3,3′‐diaminobenzidine with 1,12‐dodecanediol in 1 : 1–1:3 molar ratios in the presence of RuCl₂(PPh₃)₃ catalyst give poly(alkylenebenzimidazole), [ (CH₂)₁₁ O (CH₂)₁₁ Im / (CH₂)₁₀ Im ]_n (Im: 5,5′‐dibenzimidazole‐2,2′‐diyl) (I_a‐I_d) in 71–92% yields. The relative ratio between the [(CH₂)₁₁ O (CH₂)₁₁ Im ] unit (A) and the [‐ (CH₂)₁₀ Im ] unit (B) in the polymer chain varies depending on the ratio of the substrates used. The polymer I_a obtained from the 1 : 3 reaction contains these structural units in a 98 : 2 ratio. The polymers are soluble in polar solvents such as DMF (N,N‐dimethylformamide), DMSO (dimethyl sulfoxide), and NMP (N‐methyl‐2‐pyrrolidone) and have molecular weights M_n (M_w) of 4,200–4,800 (4,800–6,500) by GPC (polystyrene standard). The polymerization of the diol and 3,3′‐diaminobenzidine in higher molar ratios leads to partial cross‐linking of the resulting polymers I_e and I_f via condensation of imidazole NH group with CH₂OH group. Similar reactions of 3,3′‐diaminobenzidine with α,ω‐diols, HO(CH₂)_mOH (m = 4–10), in a 1 : 3 molar ratio give the polymers containing [ (CH₂)_m−1 O (CH₂) _m−1 Im ] and [ (CH₂) _m−2 Im ] units with partial cross‐linked structures. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1383–1392, 1999     

Living cationic polymerization route to poly(oligooxyethylene carbonate) vinyl ethers

The addition of dialkyl (R = Me or Et) carbonates to poly(oxyethylene)-based solid polymeric electrolytes resulted in enhanced ionic conductivities. Relatively high conductivities in lithium batteries with solutions of lithium salts in di(oligooxyethylene) carbonates such as R( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR (R = Et, n = 1, 2, or 3, m = 0, 1, 2, or 3) and related carbonates were obtained. In this respect, related comb-shaped poly(oligooxyethylene carbonate) vinyl ethers of the type  CH₂CH(OR) were prepared [R = ( OCH₂ CH₂ )_nOC(O) O ( CH₂CH₂O )_mR′; (1) n = 2 or 3, m = 0, R′ = Et; (2) n = 2 or 3; m = 3, R′ = Me]. The direct preparation of derived target polymers of this class by polymerization of the corresponding vinyl ether-type monomers could not be achieved because of a rapid in situ decarboxylative decomposition of these monomers (as formed) during the final step of their synthesis. Instead, a prepolymer was prepared by a living cationic polymerization of CH₂CH (OCH₂CH₂ )_n O C(O) CH₃ (n = 2 or 3). The hydrolysis of its pendant ester groups, followed by the reaction of the hydrolyzed prepolymer with each of several alkyl chloroformates of the type Cl C(O) O( CH₂CH₂O )_mR′ (m = 0, 2, or 3, R′ = Me or Et) resulted in the corresponding target polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2171–2183, 2002     

Supramolecular hexagonal structure of a segmented liquid crystalline polyester with allyl group as lateral substituent

The molecular structure of the phase—stable at room temperature—for the polymer with formula [ p C₆H₄ COO p C₆H₃(R) p C₆H₃(R) OOC p C₆H₄ O (CH₂)₁₀O ]_x, with R =  CH₂ CHCH₂, is reported. The cell is hexagonal (a = b = 13.43 Å, c = 33.3 Å, γ = 120°), space group P6₃, six chains per unit cell (d_calcd = 1.23 g cm⁻³). The six chains are packed together to give a bundle with the center of mass set at the origin of the unit cell. The allyl groups are placed inside the bundle, thus explaining the unexpected reactivity of the double bonds to give crosslinking when fiber samples are annealed in the solid state. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1601–1607, 1999     

Unusual formation of a λ 6P-tetrafluorophosphate involving intramolecular donor–acceptor interaction; x-ray crystal structure analysis and temperature-dependent NMR-spectra

The N,N,N′-trimethylethylenediaminetetrafluorophosphate, 4 , was formed in the unusual reaction of N,N,N′-trimethyl-N′-trimethylsilylethylenediamine, 1 , with the N P-bonded tetrafluorophosphoranes, dimethylaminotetrafluorophosphorane, 2 , or morpholinotetrafluorophosphorane, 3 . There was no evidence for the cleavage of a P F bond in the tetrafluorophosphoranes (with formation of Me₃SiF); instead, the Si N compounds, R₂N SiMe₃ (R₂ = Me₂ or O(CH₂CH₂)₂) were formed. The ¹⁹F and ³¹P NMR spectra of 4 at room temperature indicated dynamic behavior. The X-ray crystal structure analysis of 4 revealed the presence of a five-membered ring, formally as a result of intramolecular donor–acceptor interaction (P N = 196.5 pm) between the nitrogen atom of the Me₂N group and phosphorus.     

New dithiazinanes and bis‐dithiazinanes‐bearing pendant ethylamines: Structure and reactivity

The structure and reactivity of a series of new ethylaminedithiazinanes and bis‐diethylaminedithiazinanes synthesized from formaldehyde, NaSH, and N,N‐dimethyl‐ethylene‐diamine ( 1 ), N‐methyl‐ethylene‐diamine ( 2 ), and N‐ethyl‐ethylene‐diamine ( 3 ) are reported. Compound 1 afforded 2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene‐N,N‐dimethyl‐amine ( 4 ). The reaction of 4 with dry CH₂Cl₂ gave N‐{2‐([1,3,5]dithiazinan‐5‐yl)‐ethylene}‐N‐chloromethyl‐N,N‐dimethyl‐ammonium chloride ( 5 ) in high yield, whereas in wet CH₂Cl₂ and DMSO provided a mixture of 5 with N‐{2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene}‐N,N‐dimethyl‐ammonium hydrochloride ( 6 ).bis‐{2‐([1,3,5]‐Dithiazinan‐5‐yl)‐ethylene‐N‐alkyl‐amino}‐methylene‐disulfides ( 7 ) and ( 8 ) formed by two dithiazinanes linked through the chain  (CH₂)₂ NRCH₂ S S CH₂ NR (CH₂)₂‐ ( 7 R = methyl, 8 R = ethyl) reacted with CH₂Cl₂ giving after neutralization of the hydrolysis products the ethylaminedithiazinanes with different pendant N‐groups [ (CH₂)₂NMeH₂⁺( 9 );  (CH₂)₂NEtH₂⁺ ( 10 );  (CH₂)₂NMeH ( 11 );  (CH₂)₂NEtH ( 12 );  (CH₂)₂NMeHBH₃ ( 13 )  (CH₂)₂NEtHBH₃ ( 14 ).  (CH₂)₂NMe₂BH₃ ( 15 ), and  (CH₂)₂NEtMeBH₃.( 16 )]. The x‐ray diffraction analyses of compounds 5 , 6 , 9 , and 10 are reported. Variable temperature NMR experiments afforded the Δ G^≠ of the ring interconversion of the six‐membered heterocycles 6 , 9 , and 10 . © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:59–71, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20657     

Unexpected behavior of the 3JCH coupling constant in unsaturated compounds

The experimental and theoretical behavior of the (OC) CC H ³J_CH coupling constant is investigated for a series of α,β-unsaturated compounds ( 1 to 8 ), and for some of them, the well-known relationship (³J_CHcis < ³J_CHtrans) was observed. However, for some compounds, close values for ³J_CHcis and ³J_CHtrans couplings were observed, and for aldehydes group containing compounds ( 7 and 8 E), an inversion order is observed (³J_CHcis > ³J_CHtrans). In all cases where the ³J_CHcis < ³J_CHtrans relationship it is not followed, a polar group or electronegative atom oriented in opposite direction (s-trans) to the H CC hydrogen is present, suggesting that conformational preference of such polar group or atoms are important factor on the behavior of ³J_CH couplings. Taking all of these in consideration, a new Karplus-type equation was proposed for ³J_CH couplings in α,β-unsaturated compounds, which can be used for configurational and conformational assignment on trisubstituted double bond derivatives.