Selective single ring-opening polymerization of spiroorthoesters with aluminium (III) acetylacetonate

A spiroorthoester, 2-methyl-1,4,6-trioxaspiro[4.6]undecane ( 1 ), was polymerized with aluminium (III) acetylacetonate as a catalyst. The resulting polymer structure was analyzed in detail by FT-IR and 270 MHz ¹H NMR, and consisted of poly(orthoester) which was obtained by selective ring-opening of the seven-membered ring. In contrast, 2-methyl-1,4,6-trioxaspiro[4.5]decane ( 2 ) and 2-methyl-1,4,6-trioxaspiro[4.4]nonane ( 3 ) did not afford any polymers. The reactivity difference of these monomers was discussed in terms of their strain energies on the basis of MM2 calculations.     

Cationic ring-opening transfer polymerization of spiro ortho esters initiated by carbon black

The ring-opening transfer polymerization of spiro ortho esters (SOE) initiated by carbon black was investigated. In the absence of carbon black, no polymerization occurred at all. In the presence of channel black containing carboxyl group, the ring-opening transfer polymerization of SOE was initiated at 50-70°C. to give polyether ester, namely alternating copolymer of epoxide and lactone. The rate of polymerization of 1,4,6-trioxaspiro[4.4]nonane and 1,4,6-trioxaspiro[4.5]decane was considerably small compared with that of 1,4,6-trioxaspiro[4.6]undecane. The activation energy of the polymerization of 2-chloromethyl-1,4,6-trioxaspiro[4.6]undecane was estimated to be 6.0 kcal/mol. The initiating activity of carbon black increased with an increase in carboxyl group content of carbon black. Furnace black that contained no carboxyl group was unable to initiate the polymerization. Furthermore, the carbon black lost the initiating ability of the polymerization upon the blocking of carboxyl group on the surface by the treatment with potassium hydroxide or diazomethane. Based on these results, it was concluded that carboxyl group on carbon black plays an important role in the initiation. During the polymerization, a part of the polymer formed was grafted onto carbon black: the grafting ratio was 10–30%. The mechanisms of initiation and grafting were discussed.     

Synthesis and polymerization of 2-butyl-7-methylene-1,4,6-trioxaspiro(4,4)nonane

2-Butyl-7-methylene-1,4,6-trioxaspiro(4,4)nonane ( 7 ) was prepared by the reaction of 2-(bromomethyl)-5-oxo-tetrahydrofuran with 1,2-epoxyhexane, followed by dehydrobromination. Compound 7 could be polymerized by free radical initiators to give a viscous polymer. The IR and NMR spectra of the polymers indicated that the polymer structure contained ester and ketone units in the backbone, and a cyclic acetal side chain. Compound 7 readily copolymerized with acrylonitrile in the presence and absence of radical initiators, but did not copolymerize well with styrene. Ultraviolet spectra suggest that the spontaneous polymerization proceeds via a chargetransfer complex between 7 as an electron donor and AN as an electron acceptor.     

Copolymerization of unsaturated spiro ortho esters with maleic acid derivatives

The formation of charge-transfer (CT) complexes of unsaturated spiro ortho esters such as 2-methylene-1,4,6-trioxaspiro[4.4]nonane(I) and 2-methylene-1,4,6-trioxaspiro[4.6]undecane(II) with maleic acid derivatives such as maleic anhydride (Manh), dimethyl maleate (DMM), and N-ethyl maleimide (NEM) was ascertained by ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopy. The stoichiometries of these complexes were estimated as 1:1. The determination of their equilibrium constants (K) was attempted by using the Hanna-Ashbough equation with NMR spectroscopy. Although K values for I-DMM and II-DMM were specified as 0.266 and 0.336 L/mol, respectively, those for the other systems could not be obtained but were assumed to be negligible small (K ? 1). Copolymerization of these systems which was carried out without an initiator determined that spontaneous copolymerization occurs in all cases but that the copolymerization rates of I-DMM and II-DMM systems are slow. The systems in which Manh or DMM was used as an acceptor monomer gave the alternating copolymers at various monomer to feed ratios. The terpolymerizaton of the I–Manh–DMM system established that DMM takes little part in giving the alternating copolymers I and Manh. Consequently, it was assumed that the reactivity of the CT complex monomer is dependent on the contribution of the dative structure to CT complex.     

Syntheses and crosslinking reactions of polymers containing spiroorthoester moieties

The radical copolymerization of unsaturated spiroorthoesters such as 2-methylene-1,4,6-trioxaspiro[4.6]undecane (SOE I) and 2-methylene-9-methyl-1,4,6-trioxaspiro[4,5]decane (SOE II) with vinyl monomers was carried out to find that SOE I and SOE II were copolymerized with electron-poor olefins such as methyl acrylate, acrylonitrile, and methyl methacrylate to obtain the corresponding copolymers containing spiroorthoester moieties, respectively. The obtained copolymers were treated with BF₃.OEt₂ or BzS⁺SbF to afford crosslinked polymers undergoing expansion in volume on crosslinking in those cases of copolymers of SOE I.     

Synthesis and polymerization of 8,9-benzo-2-methylene-1,4,6-trioxaspiro[4,4]nonane (BMTN)

8,9-Benzo-2-methylene-1,4,6-trioxaspiro[4,4]nonane (BMTN) was prepared by the reaction of phthalide with epichlorohydrin, followed by dehydrochlorination. BMTN was polymerized with di-t-butyl peroxide (DTBP) to give a solyble polymer with a high molecular weight and good thermal stability. The infrared (IR) and nuclear magnetic resonance (NMR) spectra indicated that the polymer structure contained aromatic ester and ketone in the backbone. T_g and T_m of homopolymer of BMTN were, respectively, 98 and 282°C. BMTN was also readily copolymerized with such vinyl monomers as methyl methacrylate (MMA), acrylonitrile (AN), and maleic anhydride (MA), but not with styrene, in the presence of radical initiators. AN and MA, in particular, were spontaneously copolymerized with BMTN in the absence of radical initiators at 40°C. From the results of ultra violet (UV) spectra it is suggested that spontaneous copolymerization proceeds via a charge-transfer complex between BMTN as an electron donor and AN or MA as an acceptor.     

Synthesis of dimethyl gloiosiphone a by way of palladium-catalyzed domino cyclization

The synthesis of a spiro[4.4]nonane skeleton by the palladium-catalyzed domino cyclization of a linear 7-methylene-2,10-undecadienyl acetate is described. The pi-allylpalladium intermediate underwent intramolecular alkene insertion with high intraannular diastereoselectivity, followed by intramolecular Heck-type cyclization, leading to a spiro[4.4]nonane system. Oxidation of the allylic ether moiety and transformation of the vinyl group to an exo-methylene unit provided 3, which is the known synthetic intermediate of dimethyl gloiosiphone A (2).     

SYNTHESIS AND FREE RADICAL RING-OPENING POLYMERIZATION OF 2-METHYL-AND 2-METHYL-9-n-BUTYL-(-7-METHYLENE-1,4,6-TRIOXA-SPIRO (4, 4)NONANE)

This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by IR, 'H and ~(13)C NMR spectra. The substituent on 9-position of 7-methylene-trioxaspiro (4, 4) nonane affects the structure of polymer and polymerization activity. The polymerization mechanism is discussed.     

Mecanisme de formation et de transformation des spirophosphoranes—IX: Reactions des spirophosphoranes a liaison PH avec les ethers vinyliques et les enamines

The reaction of 1,4,6,9-tetraoxa-5-phospha(V)spiro[4,4]nonane 1 with ethyl vinyl ether gives a spirophosphorane containing a PC bond, 5-(β-ethosyethyl)-1,4,6,9-tetra-oxa-5-phospha(V) spiro[4,4]nonane 2 (radical reaction), and a tricoordinated phosphorus compound, 2-(3,5-di-oxa-4-methylheptanoxyl)-1,3,2-dioxaphospholane 3 (ionic reaction). 2,2,3,3,7,7,9-Heptamethyl-1,4,6-trioxa-9-aza-5-phospha(V) spiro[4,4]nonane 6 gives exclusively a spirophosphorane containing a PC bond, 5(β-ethoxyethyl)-2,2,3,3,7,7,9-heptamethyl-1,4,6-trioxa-9-aza-5-phospha(V)spiro[4,4]nonane 7. The reaction of 1 with alcohol or ethyleneglycol and enamine yields a pentaoxyspirophosphorane and an amine by an oxidation-reduction condensation. Suggested mechanisms of these reactions are presented.     

Synthesis and Structure of 8-Methyl-2-methylene-1,4,6,9-tetraoxaspiro[4.4]nonane

By reacting propylene carbonate with epichlorohydrin 8-methyl-2-chloromethyl-1,4,6,9-tetra- oxaspiro[4.4]nonane was obtained that afforded 8-methyl-2-methylene-1,4,6,9-tetraoxaspiro[4.4]nonane on dehydrochlorination. The spirocompounds synthesized are composed of stereoisomers mixtures containing: cis,syn-, cis,anti-, trans,syn-, trans,anti-isomers and cis,syn-, cis,anti-isomers, respectively. These isomers are distinguished by a different orientation of substituents in positions 2 and 8 with respect to two five-membered rings.     

Novel silicon‐containing spiroorthoester to confer combined flame retardancy and low shrinkage properties to epoxy resins

A new silicon‐containing spiroorthoester, 1,4,6‐trioxaspiro [4,4]‐2‐nonylmethyl 3‐trimethylsilyl propionate (SOE? Si), was synthesized with good yield by an esterification reaction with a previously synthesized 2‐hydroxymethyl‐1,4,6‐trioxaspiro [4,4] nonane (SOE? OH) and trimethylsilyl propionic acid. The structure of the new SOE? Si was confirmed by ¹H and ³C NMR. The SOE? Si and a mixture of DGEBA/SOE? Si were polymerized with ytterbium triflate as a cationic initiator. The curing was studied with differential scanning calorimetry (DSC) and monitored by Fourier transform infrared (FTIR) spectroscopy. The materials were characterized with DSC, termogravimetric analysis (TGA) and thermodynamomechanical analysis (DMTA). The volume change was evaluated with a Micromeritics gas pycnometer and the flame retardancy was tested by the limiting oxygen index (LOI) measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4211–4224, 2007     

Phosphorus-containing thermosets obtained by cationic copolymerisation of glycidyl compounds with a spiroorthoester or γ-butyrolactone

The synthesis of a bis[(1,4,6-trioxaspiro[4.4]nonan-2-yl)-methyloxy] ethane (bisSOE) and its copolymerisation with mixtures of diglycidyl ether of bisphenol A (DGEBA) and different phosphorus-containing glycidyl compounds led to materials with enhanced flame retardancy and low shrinkage on crosslinking. Analogous materials were obtained by reaction of mixtures where the spiroorthoester (SOE) is formed in the reaction medium from γ-butyrolactone and a diglycidyl compound.The incorporation of phosphorus in the networks increases the LOI values and all crosslinked polymers showed a slight shrinkage after curing, much lower than that observed in conventional epoxy resins. The materials from preformed SOE showed lower shrinkage than the analogues from lactone and epoxy groups.     

Polymerization of cyclic monomers, 1. Radical polymerization of unsaturated spiro orthocarbonates

7-Methyl-2-methylene- ( 1 ) and 7-methyl-2,3-dimethylene-1,4,6,9-tetraoxaspiro[4.4]nonane (2) were synthesized and characterized by elemental analysis, IR, ¹H NMR and ¹³C NMR spectroscopy. Radical polymerization of the spiro orthocarbonates (SOC) 1 and 2 show that they undergo primarily vinyl polymerization with a low degree of ring-opening reaction. Homopolymerization of 2 at 120°C with di-tert-butyl peroxide gives a transparent crosslinked polymer and the polymerization generates a 12,5% shrinkage in volume.     

Synthesis of a novel bis‐spiroorthoester containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐oxide as a substituent: Homopolymerization and copolymerization with diglycidyl ether of bisphenol A

A new bis‐spiroorthoester‐containing monomer, bis[(1,4,6‐trioxaspiro‐[4.4]‐nonan‐2‐yl)‐methyl] 2‐[10‐(9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐oxide‐10‐yl)] maleate (SOE‐DOPOMA), was synthesized with good yields by an esterification reaction with a hydroxylated spiroorthoester (2‐hydroxymethyl‐1,4,6‐trioxaspiro‐[4.4]‐nonane) and a phosphorus‐containing diacid {2‐[10‐(9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐ oxide‐10‐yl)] maleic acid}, both of which were previously synthesized. SOE‐DOPOMA was characterized with ¹H, ¹³C, and ³¹P NMR spectroscopy. This new spiroorthoester was crosslinked with ytterbium triflate as a cationic initiator. A mixture of SOE‐DOPOMA and diglycidyl ether of bisphenol A was also crosslinked under the same conditions. The curing was studied with differential scanning calorimetry and monitored with Fourier transform infrared spectroscopy. The materials were characterized with differential scanning calorimetry, thermogravimetric analysis, and thermodynamomechanical analysis. The shrinkage effect on cationic crosslinking was assessed with gas pycnometry, and the flame‐retardant properties were determined with limiting oxygen index measurements. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1980–1992, 2007.     

Ring opening reactions of 6-oxo-substituted spiro-pyrrolidinediones: Synthesis of 4-substituted-1,5-dihydro-3-hydroxy-2-oxo-1,5-diphenyl-2H-pyrroles

Reaction of 2-oxocylalkaneglyoxylate esters with N-phenylmethyleneaniline yields spiro compounds such as 2-aza-3,4,6,-trioxo-1,2-diphenylspiro[4.4]nonane 4 and cycloalkane-2-aza-3,4,6-trioxo-1,2-diphenylspiro-[4.5]decanes 5–7 . These undergo solvolytic opening of the the oxocycloalkane ring to yield 4-substituted-1,5-dihydro-3-hydroxy-2-oxo-1,5-diphenyl-2H-pyrroles 12–17 .     

Organoboron compounds : CCCXCIX. The matteson-pasto rearrangement in the series of 3-borabicyclo[3.3.1]nonane compounds

Bromination of 3-isopropyl-7-methyl- and 3-isopropyl-7-bromomethyl-3-borabicyclo[3.3.1]nonane leads to corresponding 3-(2-bromo-2-propyl) derivatives, which, on treatment with alcohols or pyridine as well as on heating, undergo the Matteson-Pasto rearrangement to convert into 3-X-4,4,8-trimethyl- and 3-X-4,4-dimethyl-8-bromomethyl-3-borabicyclo[4.3.1]decane (X = Br, OR). Interaction between triethylamine and 3-(2-bromo-2-propyl)-7-methyl-3-borabicyclo[3.3.1]nonane is accompanied by dehydrobromination leading to 3-isopropenyl-7-methyl-3-borabicyclo[3.3.1]nonane. Carbonylation of 3,4,4,8-tetramethyl-3-borabicyclo[4.3.1]decane at 140°C is accompanied by migration of two alkyl groups from the boron to the carbon atom, and subsequent oxidation with H₂O₂ produces 1-(2-hydroxy-2-methyl-1-propyl)-3-acetonyl-5-methyl-cyclohexane. Under more forcing conditions (180-195°C), the third alkyl group also migrates to give, after oxidation, a mixture of isomeric 3,4,4,8-tetramethylbicyclo[4.3.1]decan-3-ols. 3-n-Butoxy-4,4-dimethyl-8-bromomethyl-3-borabicyclo[4.3.1]decane, on treatment with Lì, undergoes cyclization to afford 4,4-dimethyl-3-borahomoadamantane, carbonylation and subsequent oxidation of which gave 4,4-dimethylhomoadamantan-3-ol.     

Synthesis and photochemical reaction of cyclic oligomers: Synthesis and photopolymerization of novel C‐methylcalix[4]resorcinarene and p‐alkylcalix[n]arene derivatives containing spiro ortho ether groups

New photoreactive calixarene derivatives containing spiro ortho ester groups (calixarenes 3a–3c ) were synthesized by the reaction of 2‐bromomethyl‐1,4,6‐trioxaspiro[4.4]nonane with 2,8,14,20‐tetramethyl‐4,6,10,12,16,18,22,24‐octakis(carboxymethoxy)calix[4]resorcinarene, 5,11,17,23,29,35‐hexamethyl‐37,38,39,40,41,42‐hexakis(carboxymethoxy)calix[6]arene, and 5,11,17,23,29,35,41,47‐octa‐tert‐butyl‐49,50,51,52, 53,54,55,56‐octakis‐(carboxymethoxy)calix[8]arene, which were prepared by the reaction of C‐methylcalix[4]resorcinarene, p‐methylcalix[6]arene, and p‐tert‐butylcalix[8]arene, respectively. The thermal stability of the obtained calixarene derivatives containing spiro ortho ester groups was examined with thermogravimetric analysis, and it was found that these calixarene derivatives had good thermal stability. The photoinitiated cationic polymerization of spiro ortho ester groups in calixarene derivatives 3a–3c was examined with certain photoacid generators in the film state. Interestingly enough, the reaction of calixarene derivatives did not proceed with only photoirradiation; however, the reaction proceeded smoothly when the photoirradiation was followed by heating. Furthermore, calixarene 3a , composed of a C‐methylcalix[4]resorcinarene structure, showed the highest photochemical reactivity in this reaction system. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1293–1302, 2002     

Synthesis of 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane, 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane, and 2-(pyridin-3-yl)-1-azabicyclo[3.2.1]octane, a class of potent nicotinic acetylcholine receptor-ligands

In an attempt to generate nicotinic acetylcholine receptor (nAChR) ligands selective for the alpha4beta2 and alpha7 subtype receptors we designed and synthesized constrained versions of anabasine, a naturally occurring nAChR ligand. 2-(Pyridin-3-yl)-1-azabicyclo[2.2.2]octane, 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane, and several of their derivatives have been synthesized in both an enantioselective and a racemic manner utilizing the same basic synthetic approach. For the racemic synthesis, alkylation of N-(diphenylmethylene)-1-(pyridin-3-yl)methanamine with the appropriate bromoalkyltetrahydropyran gave intermediates which were readily elaborated into 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane and 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane via a ring opening/aminocyclization sequence. An alternate synthesis of 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane via the alkylation of N-(1-(pyridin-3-ylethylidene)propan-2-amine has also been achieved. The enantioselective syntheses followed the same general scheme, but utilized imines derived from (+)- and (-)-2-hydroxy-3-pinanone. Chiral HPLC shows that the desired compounds were synthesized in >99.5% ee. X-ray crystallography was subsequently used to unambiguously characterize these stereochemically pure nAChR ligands. All compounds synthesized exhibited high affinity for the alpha4beta2 nAChR subtype ( K i < or = 0.5-15 nM), a subset bound with high affinity for the alpha7 receptor subtype ( K i < or = 110 nM), selectivity over the alpha3beta4 (ganglion) receptor subtype was seen within the 2-(pyridin-3-yl)-1-azabicyclo[2.2.2]octane series and for the muscle (alpha1betagammadelta) subtype in the 2-(pyridin-3-yl)-1-azabicyclo[3.2.2]nonane series.     

The reaction of perfluorobicyclic ethers and perfluorospiro-ethers with anhydrous aluminum chloride

Perfluorobicyclic ethers and perfluorospiroethers, all containing an oxolane skeleton, were treated with AlCl₃ in a heterogeneous manner to give the corresponding α,α,α′-trichlorinated and α,α-dichlorinated products, respectively. From perfluoroacetal compounds, for example, perfluoro(8-methoxy-7-oxabicyclo- [4.3.0]nonane), mono- and di-chlorinated products, i.e. perfluoro- (8-chloro-8-methoxy-7-oxabicyclo[4.3.0]nonane) and perfluoro- (8,8-dichloro-7-oxabicyclo[4.3.0]nonane) were obtained in good yields. The action of fuming sulfuric acid on these polychlorinated products led to the formation of the corresponding lactones. Perfluoro(6-chloro-7-oxa-8-oxobicyclo[4.3.0]nonane) was treated with (CH₃)₂NLi to give N,N-dimethylundecafluoro-2-oxocyclohexyl- acetamide.     

Synthesis and cationic ring-opening polymerization of mono- and bifunctional spiro orthoesters containing ester groups and depolymerization of the obtained polymers: An approach to chemical recycling for polyesters as a model system

A spiro orthoester having an ester moiety, 2-acetoxymethyl-1,4,6-trioxaspiro[4.6]undecane (4) was synthesized, and its cationic polymerization and depolymerization of the obtained polymer (5) were carried out. The monomer 4 underwent cationic polymerization with a cationic catalyst to afford the corresponding poly(cyclic orthoester) 5. The obtained polymer 5 could be depolymerized with a cationic catalyst to regenerate the monomer 4 in an excellent yield. Further, bifunctional spiro orthoesters (6, 8, 9) having diester moieties were synthesized from terephthalic acid, succinic acid, and 1,4-cyclohexanedicarboxylic acid, and their acid-catalyzed reversible crosslinking–decrosslinking was examined. The bifunctional monomer 6 derived from terephthalic acid underwent cationic crosslinking to afford the corresponding network polymer (7), which could be also depolymerized to regenerate the original bifunctional monomer 6. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2551–2558, 1999