Cationic copolymerization of phenyl propenyl ethers

Ring-substituted phenyl propenyl ethers were found to form homopolymers without any rearrangement by metal halides. Phenyl propenyl ethers were less reactive than the corresponding phenyl vinyl ethers in cationic polymerization. In order to study the electronic effect of a substituent on the reactivity, cis-p-Cl,p-CH₃, and p-CH₃O-phenyl propenyl ethers were copolymerized with phenyl propenyl ether in methylene chloride at ?78°C with stannic chloride–trichloroacetic acid, and their ¹H- and ¹³C-NMR spectra were measured. The reaction constant ρ against Hammett σ_p was ?2.1. The cis-phenyl propenyl ethers were slightly more reactive than the corresponding trans isomers. On the other hand, an o-methyl group decreased the reactivity of phenyl propenyl ether. The low reactivity of o-methyl phenyl propenyl ether was attributed to the steric hindrance between the propagating carbocation and the monomer.     

Kinetik und stereochemischer Verlauf der thermischen Umlagerung der vier stereoisomeren Propenyl-(but-2′-enyl)-äther

The gas-phase rearrangement of (1Z, 2′E)-, (1Z, 2′Z)-, (1E, 2′E)-, and (1E, 2′Z)- propenyl but-2′-enyl ether (Z, E)-, (Z, Z)-, (E, E)-, and (E, Z)-1) into erythro- and threo-2, 3-dimethyl-pent-4-en-al (erythro- and threo-2) was investigated over a temperature range from 142,5° to 190,0° at 20–35 Torr (for kinetic data and activation parameters see table 2). All four stereoisomeric ethers 1 rearrange preferentially via a chair-like transition state C into the aldehydes 2 (ΔΔG^≠ (160°) = 2,5–2,7 kcal/mol for B – C (B = boat-like transition state). The relative rates (k_rel) for (Z, Z)-1, (Z, E)-1, (E,Z)-1, and (E,E)-1 at 160° are 1,0, 2,9, 4,3 and 9,0 respectively (see table 5). Taking into account the relative enthalpies of the ethers 1 and the steric interaction in the C transition state of the ethers 1 (see table 6), k_rel values can be estimated. They are in good agreement with those observed (see table 5).     

Stereochemistry in cationic polymerization of alkenyl ethers. III. Effect of the alkoxy group on the steric structure of polymers

Propagation mechanism in the cationic polymerization of alkenyl ethers was investigated through the effect of the bulkiness of alkoxy groups on the steric structure of a polymer. In polymerization with BF₃O(C₂H₅)₂ in toluene at ?78°C, trans-propenyl ethers having less bulky alkoxy groups–methyl, ethyl, and benzyl propenyl ethers–produced a stereoregular polymer having a threo-meso structure, and the cis isomer a nonstereoregular one having threo-meso and racemic structures. On the other hand, in the polymerization of propenyl ethers having bulky alkoxy groups–isopropyl and 1-methylpropyl propenyl ethers–the trans isomer yielded a nonstereoregular polymer with threo-meso and racemic structures, and the cis isomer a stereoregular one with a erythro-meso structure. This result suggests that a bulky alkoxy group plays an important role in determining the steric structure of the polymer by repulsion between the alkoxy groups of a growing chain end and of a monomer. The effect of solvent polarity on the steric structure of a polymer was also studied.     

Cationic polymerization of α,β-disubstituted olefins. V. Reactivity of propenyl alkyl ethers in cationic polymerization

To elucidate the effect of the introduction of a methyl group in the β-position of a vinyl monomer, propenyl alkyl ethers were copolymerized with vinyl ethers having the same alkoxy group. Propenyl alkyl ethers with an unbranched alkoxy group (ethyl or n-butyl propenyl ether) were more reactive than the corresponding vinyl ethers. This behavior is quite different from that of β-methylstyrene derivatives. However, propenyl alkyl ethers with branched alkoxy groups at the α carbon atom (isopropyl or tert-butyl propenyl ether) were less reactive than the corresponding vinyl ethers. Also, cis- isomers were more reactive than the trans isomers, regardless of the kind of alkoxy group and the polarity of the solvent.     

Bemerkung zur vorstehenden Notiz [1] von H. REMBOLD

The possible transition state conformations (chair (S), boat (W), and twist (T), respectively cross (K) forms) and methods for their determination in the thermal ortho-CLAISEN rearrangement of allyl aryl ethers are discussed. Crotyl 3,5-dimethylphenyl ether ( 11 ) gives a mixture of 2-(α-methylallyl)-3,5-dimethyl-phenol ( 12 ) and 4-crotyl-3,5-dimethyl-phenol ( 13 ) on heating in N, N-diethylaniline. Values of 3 and 31 were obtained for the ratio of 12 / 13 for trans- 11 and cis- 11 , respectively. It therefore follows that both ethers rearrange steroselectively ( > 90%) by the S or W forms of the activated complex. αMethylallyl 6-alkylphenyl ethers rearrange on heating in various solvents to a mixture of trans-and cis-2-crotyl-6-alkyl-phenols. The amount of the cis-phenols in the rearrangement products decreases with the increasing bulk of the 6-alkyl substituent. This result is only obvious if the chair form of the transition state during the rearrangement of these ethers is highly favoured. trans-Crotyl 2,6-dimethylphenyl ether (trans- 33 ) rearranges highly steroselectively (94%) on heating to trans-4-crotyl-2,6-dimethyl-phenol (trans- 34 ). In the case of the corresponding cis ether 33 , the rapid cis → trans isomerisation of this ether and the cis/trans ratio of the phenol 34 indicate that the reverse rearrangement of the intermediate ortho-dienone to the ether 33 and the further rearrangement to 4-crotyl-2,6-dimethyl-phenol ( 34 ) has little stereoselective character.     

Stereochemistry in cationic polymerization of alkenyl ethers. II. Formation of poly(ß-substituted vinyl ether)s with erythro-meso structures

The formation of polymers with erythro-meso structures, which could not be obtained from propenyl ethers with BF₃O(C₂H₅)₂, was studied by ¹³C-NMR spectroscopy on poly(ß-substituted vinyl ether)s obtained under a variety of conditions of polymerization. It was established that poly(cis-ethyl propenyl ether) obtained with Al₂(SO₄)₃–H₂SO₄ complex in toluene at 0°C was a highly stereoregular polymer with an erythro-meso structure. Cis-2-chlorovinyl ethyl ether and cis-methyl and ethyl butenyl ethers also yielded polymers with erythro-meso structures under the same conditions. In addition, with BF₃O(C₂H₅)₂ at ?78°C these three cis isomers produced amorphous polymers with threo-meso, racemic, and, in a few cases, erythro-meso structures, whereas cis-ethyl propenyl ether produced polymers with only threo-meso and racemic structures by the same catalyst. On the other hand, all trans isomers produced stereoregular polymers with threo-meso structures with BF₃O(C₂H₅)₂ at ?78°C, regardless of their ß-substituents; no erythro-meso structures were found in the polymers obtained.     

Living cationic polymerization of α‐methyl vinyl ethers using SnCl4

Cationic polymerization of α‐methyl vinyl ethers was examined using an IBEA‐Et_1.5AlCl_1.5/SnCl₄ initiating system in toluene in the presence of ethyl acetate at 0 ～ ?78 °C. 2‐Ethylhexyl 2‐propenyl ether (EHPE) had a higher reactivity, compared to corresponding vinyl ethers. But the resulting polymers had low molecular weights at 0 or ?50 °C. In contrast, the polymerization of EHPE at ?78 °C almost quantitatively proceeded, and the number‐average molecular weight (M_n) of the obtained polymers increased in direct proportion to the EHPE conversion with quite narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ 1.05). In monomer‐addition experiments, the M_n of the polymers shifted higher with low polydispersity as the polymerization proceeded, indicative of living polymerization. In the polymerization of methyl 2‐propenyl ether (MPE), the living‐like propagation also occurred under the reaction conditions similar to those for EHPE, but the elimination of the pendant methoxy groups was observed. The introduction of a more stable terminal group, quenched with sodium diethyl malonate, suppressed this decomposition, and the living polymerization proceeded. The glass transition temperature of the obtained poly(MPE) was 34 °C, which is much higher than that of the corresponding poly(vinyl ether). This poly(MPE) had solubility characteristics that differed from those of poly(vinyl ethers). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2202–2211, 2008     

Cationic polymerization of α,β-disubstituted olefins. IV. Stereospecific polymerization of propenyl alkyl ethers catalyzed by BF3·O(C2H5)2 and Al2(SO4)3–H2SO4 complex

The cis- and trans-propenyl alkyl ethers were polymerized by a homogeneous catalyst [BF₃·O(C₂H₅)₂] and a heterogeneous catalyst [Al₂(SO₄)₃–H₂SO₄ complex]. Methyl, ethyl, isopropyl, n-butyl and tert-butyl propenyl ethers were used as monomers. The steric structure of the polymers formed depended on the geometric structures of monomer and the polymerization conditions. In polymerizations with BF₃·O(C₂H₅)₂ at ?78°C., trans isomers produced crystalline polymers, but cis isomers formed amorphous ones except for tert-butyl propenyl ether. On the other hand, highly crystalline polymers were formed from cis isomers, but not from the trans isomers in the polymerization by Al₂(SO₄)₃–H₂SO₄ complex at 0°C. The x-ray diffraction patterns of the crystalline polymers obtained from the trans isomers were different from those produced from the cis isomers, except for poly(methyl propenyl ether). The reaction mechanism was discussed briefly on these basis of these results.     

Thermische Umlagerungen von halogensubstituierten Aryl-propargyläthern

7-Chloro-2-chloromethyl-benzofuran (13) and 3, 8-dichloro-2 H-1-benzopyran (12) are the main products from the thermal rearrangement (230–260°) of 2, 6-dichlorophenyl propargyl ether (7) . Compounds 17 , 18 and 19 are also formed, but in much smaller amounts (scheme 2 and table 1). However, in the case of the bromo-compounds 8 and 9 the rearrangement products are the benzofuran derivatives 21 and 22 , containing one bromine atom less per molecule (scheme 4). The corresponding naphthyl propargyl ethers 10 and 11 can be rearranged much more easily (180°) to the halogeno-naphthofurans 24 and 26 respectively. In the case of the bromo-ether 11 , 2-methyl-naphtho[2, 1-b]furan (25) is also formed (scheme 5). If the propargylic hydrogen atoms in 7 and 11 are replaced by deuterium atoms, then after rearrangement the deuterium atoms in the products d- 13 and d- 26 are found in the β-positions to the oxygen atom of the furan ring (schemes 3 and 5). It is suggested that initially a [3s, 3s]-sigmatropic rearrangement of the aryl propargyl ethers to the 6-allenyl-6-halogeno-cyclohexa-2, 4-dien-1-ones (e.g. a ) occurs and that from these the isolated products are formed via radical pathways (scheme 6). Under neutral conditions aryl propargyl ethers containing a free ortho-position give on heating benzopyran derivatives [2]. When this thermal reaction is carried out in sulfolane in the presence of powdered potassium carbonate, 2-methyl-benzofuran derivatives are formed (table 2). This leads to the possibility of preparing, depending on the conditions, either benzopyran or benzofuran derivatives by the Claisen rearrangement of aryl propargyl ethers. The mechanism for the formation of the benzofurans is given in scheme 9.     

Thermische Umwandlung von Penta-2, 4-dienyl-phenyläthern in 4-(Penta-2, 4-dienyl)-phenole; [5s, 5s]-sigmatropische Umlagerungen

trans-Penta-2, 4-dienyl phenyl ether (trans- 1 ), on heating at 186° in a five-fold excess of N, N-diethylaniline, gave via a [3s, 3s] rearrangement 23% of 2-(1-vinyl-allyl)-phenol ( 2 ) and via a [5s, 5s] rearrangement 37% of trans-4-(penta-2, 4-dienyl)-phenol (trans- 3 ). The dimeric residue was formed from trans- 1 by diene synthesis. By working at high dilution, the formation of dimeric products was kept to a minimum. The inversion of the migrating pentadienyl residue during the rearrangement of trans- 1 to trans- 3 was proved by rearrangement of the methyl labelled ether trans, trans- 4 to the p-dienyl-phenol 8 (93%) (accompanied by only 7% of 9 ). trans- 5 gave the p-phenol 9 quantitatively. cis-Penta-2, 4-dienyl phenyl ether (cis- 1 ) was converted to 10 on heating, by a fast [1, 5s] H-migration. The above mentioned reactions of the type trans- 1 → trans- 3 show first order kinetics and are the first examples of [5s, 5s] sigmatropic rearrangements shown to go through a ten-membered transition state. The conformation of the activated complex is discussed in the light of the stereochemistry of the migrating penta-2, 4-dienyl group.     

The infrared spectra and conformation of methyl and ethyl propenyl ethers

The infrared spectra of the cis and trans geometric isomers of methyl and ethyl propenyl ethers have been recorded in the liquid and vapour phase, in the region 4000-200 cm^?1. Solid phase spectra have also been recorded for all but trans methyl propenyl ether. Evidence is given for the existence of two rotameric forms for both the trans compounds, in each case the more stable conformer being planar s-cis; but a single non-planar conformation is suggested for the two cis isomers. The enthalpy difference between the two rotameric forms in trans ethyl propenyl ether was found to be 4.6 ± 1.0 kJ mol^?1 (1100 ± 250 cal mol^?1).     

Umlagerung von Allyl-aryläthern und Allyl-cyclohexadienonen mittels Bortrichlorid

Allyl aryl ethers which have no strongly electron attracting substituents undergo a charge-induced [3 s, 3 s] sigmatropic rearrangement in the prescence of 0.7 mole boron trichloride in chlorobenzene at low temperature, to give after hydrolysis the corresponding o-allyl phenols (Tables 1 and 2). The charge induction causes an increase in the reaction rate relative to the thermal Claisen rearrangement of ～10¹⁰. With the exception of allyl 3-methoxyphenyl ether (5) , m-substituted allyl aryl ethers show similar behaviour (with respect to the composition of the product mixture) to that observed in the thermal rearrangement (Table 3). The rearrangement of allyl aryl ethers with an alkyl group in the o-position, in the prescence of boron trichloride, yields a mixture of o- and p-allyl phenols, where more p-product is present than in the corresponding product mixture from the thermal rearrangement (Table 4). This ‘para-effect’ is especially noticeable for o-alkylated α-methylallyl aryl ethers (Table 5 ). With boron trichloride, 2,6-dialkylated allyl aryl ethers give reaction products which arise, in each case, from a sequence of an ortho-Claisen rearrangement followed by a [1,2]-, [3,3]- or [3,4]-shift of the allyl moiety (Tables 6 and 7). Ally1 mesityl ether (80), with boron trichloride, gives pure 3-ally1 mesitol ( 95 ). From phenol, penta-ally1 phenol ( 101 ) can be obtained by a total of five O-allylations followed by three thermal and two boron trichloride-induced rearrangements. The sigmatropic rearrangements of the ethers studied, using D- and ¹⁴C-labelled compounds, are collected in scheme 2; only the reaction steps indicated by heavy arrows are of importance. With protic acids, there is a [3,3]-shift of the allyl group in 6-allyl-2,6-disubstituted cyclohexa-2,4-dien-l-ones, while with boron trichloride the [3,3]-reaction is also observed along with the much less important [1,2]- and [3,4]-transformations (Table 8). 4-Allyl-4-alkyl-cyclohexa-2,5-dien-1-ones give only [3,3]-rearrangements with boron trichloride (Table 9). As expected, the naphthalenone 112 , which is formed by allowing boron trichloridc to react for a short time with allyl (1-methyl-2-naphthyl) ether ( 111 ), undergoes only a [3,4] rearrangement (Scheme 3). Representations of how, in our opinion, the complex behaviour of allyl aryl ethers and allyl cyclohexadienones under the influence of boron trichloride, can be rationalized are collected together in Schemes 4 and 5. In the last part of the discussion section, the steric factors leading to the appearance of the ‘para-effect’, are dealt with (Scheme 6).     

[2 + 2] cycloaddition of optically active ketenes. Synthesis of (−)-blastmycinone. Preliminary Communication

[2 + 2] Cycloaddition of (menthyloxy)methylketene ( 2 ) to cis-ethyl propenyl ether showed a ca. 3:1 diastereo-selectivity. A two-step transformation of the thermodynamically more stable adduct 4 furnished the (2R*, 3R*)-compound 5 with ca. 50% e.e. (Scheme 1). The analogous reaction sequence with cis- benzyl 1-hexenyl ether ( 9 ) and 2 showed a ca. 5:1 diastereoselectivity in 10 and 11 (Scheme 2). Absolute configuration of C(3) and C(4) in 11 has been proved by converting it to (?)-blastmycinone. Accordingly, the preferred transition state has been deduced as 15 .     

β-Cleavage of Bis(homoallylic) Potassium Alkoxides. Two-Step Preparation of Propenyl Ketones from Carboxylic Esters. Synthesis of ar-Turmerone, α-Damascone, β-Damascone,and β-Damascenone

The transformation of 36 bis(homoallylic) alcohols VII to alkenones IX and X via β-cleavage of their potassium alkoxides VIIa in HMPA has been investigated (cf. Scheme 2). These studies have established an order of β-cleavage for 2-propenyl, 1-methyl-2propenyl, 2-methyl-2-propenyl, 1,1-dimethyl-2propenyl, and benzyl groups in alkoxides 49a – 56a and have allowed a comparison between the β-cleavege reaction and the oxy-Cope rearrangement in alkoxides 74a – 83a . As illustrative syntheti applications, a two-step preparatio of propenyl ketones 15 – 42 from carboxylic esters is described, together with syntheses of ar-turmerone ( 48 ), α-damascone ((E)- 71 ), β-damascone ((E)- 109 ), and β-damascenone ((E)- 111 ).     

Notiz betreffend ladunsinduzierte Umlagerung von Allyl-aryläthern mit Trifluoressiǵsäure

The rearrangement of allylarylethers (allylphenylether, crotyl-4-methylphenylether) in trifluoracetic acid to the corresponding 2-allylphenols according to Svanholm & Parker [1] is shown to be of the charge-induced [3s, 3s]-type [3]. Because of the subsequent formation of cyclic ethers and other sideproducts, yields are low.     

Investigations on the question of multiple mechanisms in the cope rearrangement

The possible occurrence of the ionic Cope rearrangement, and other non-concerted mechanisms is discussed. The synthesis of 2 - (1 - ethyl - 1 - propenyl) -2- (3 - p - methoxyphenylallyl)malononitrile (1b) and its clean thermal 1,3 rearrangement to (1 - ethyl - 5 - p - methoxyphenyl - 2 - methyl - 4 - pentenylidene)malononitrile (4) are reported. This result contrasts with the rearrangement of 2 - (1,1 - dideuterioallyl) - 2 -(1 - ethyl - 1 - propenyl)malononitrile (1c) which isomerizes cleanly in a 3,3 rearrangement. Rearrangement of 2 - (1 - cyclohexenyl) - 2 - (3 - p - methoxyphenylallyl)malononitrile (11), however, leads sluggishly to [2 - (p - methoxy - α - vinylbenzyl)cyclohexylidene]malononitrile (19) (3,3 shift) and rearrangement of 2 - (1 - isopropyl - 2 - methyl - 1 - propenyl) - 2 -(3 - p - methoxyphenylallyl)malononitrile (12) leads, also slowly, to (1 - isopropyl - 5-p- methoxyphenyl - 2,2 - dimethyl - 4 - pentenylidene)malononitrile (14) (1,3 shift). Rearrangement of 1b in the presence of sodium borohydride allows interception of the proposed ionic intermediates and isolation of 2 - (1 - ethylpropylidene)malononitrile (5) and anethole (21c). Ion trapping experiments also gave positive results in the 3,3 rearrangement of 11. These results are discussed in terms of the ionic Cope rearrangement.     

Die durch Silberionen katalysierte Umlagerung von Propargyl-phenyläther

It is known that propargyl-phenylethers rearrange at about 200° to 2 H-chromenes [1–4]. It is shown that this rearrangement occurs in benzene or chloroform at lower temperatures (20–80°) in the presence of silver-tetrafluoroborate (or-trifluoracetate). The ethers examined are presented in Scheme 1. Thus in chloroform at 61° in the presence of AgBF₄, phenyl-propargylether ( 3 ) yields 2 H-chromene ( 13 ). With 0.78 molar equivalents AgBF₄ in benzene at 80° the same ether 3 yields a 3:1 mixture of 2-methyl-cumaron ( 14 ) and 2 H-chromene ( 13 ). From 1′-methylpropargyl-phenylether ( 4 ) and 2′-butinyl-3,5-dimethylphenylether ( 5 ) under similar conditions the corresponding chromenes 16 and 17 resp. are obtained. Rearrangement of propargyl- and 2′-butinyl-1-methyl-2-naphthylether ( 6 and 7 resp.) in benzene at 80° in the presence of AgBF₄ gives the corresponding allenyl-naphthalenones 18 and 19 resp. Treatment of propargyl- and 2′-butinyl-mesityl-ether ( 8 and 9 resp.), and propargyl- and l′-methylpropargyl- 2 , 6 -dimethyl-phenylether ( 10 and 11 resp.) in benzene at 80° with AgRF, yields as the only product the corresponding 3 -allenyl-phenols 21 , 22 , 24 and 25 (Scheme 3). It is shown that in the presence of μ-dichlor-dirhodiuni (1)-tetracarbonyl in benzene a t 80° the ether 4 rearranges to 2-methyl-2H-chromene (16). However with this catalyst the predominant reaction is a cleavage to phenol. No reaction was observed when ethers 3 and 12 , (Scheme 7 ) were treated with the tris-(trimethylsily1)-ester of vanadic acid in benzene a t 80° (see also [8]). By analogy with the known mechanism for thc silver catalysis of the reversible propargylesterl/allenylester rearrangement [S], the silver (1)ion is assumed to form a pre-equilibrium π-complex with the C, C-triplebond of the substrate. This complex then undergoes a [3s, 3s]-sigmatropic rearrangement (Scheme 2). In the case of the others 6 , 7 and 12 the resulting allenyldienones were isolated. The 2,G-dimethyl substituted ethers 8 , 9 , 10 and 11 resp. first give the usual allenyl- dienones (Scheme 3). These then undergo a novel silver catalysed dienon-phenol-rearrangement (Sclzenzu4) to give the 3-allenylphenols 21 , 22 , 24 and 25 . Thc others 3 , 4 and 5 with free ortho positions presumably rearrange first to the non-isolated 2-allenyl-phenols 15 , 42 and 43 resp.(Scheme 7). These then rearrange, either thermally or by silver (1)ion catalysis to the 2H-chromenes 13 , 16 and 17 resp. The rate of the rearrangement of 2-allenylphenol ( 15 ) to 13 at room temperature in benzene or chloroform is approximately doubled when silver ions are present as catalyst.     

Sigmatropische Umlagerungen von Aryl-propargyläthern; Synthese von 1, 5-Dimethyl-6-methylen-tricyclo[3, 2, 1, 02,7]-oct-3-en-8-on-Derivaten. Vorläufige Mitteilung

2, 6-Dimethylphenyl propargyl ether ( 10 ) and its derivatives 12–15 rearrange thermally to 1, 5-dimethyl-6-methylene-tricyclo [3.2.1.0^2,7]oct-3-en-8-one ( 9 ) and related compounds 16–19 . The ethers undergo first an aromatic [3, 3]-sigmatropic rearrangement to ortho-allenyldienones 11 , which then undergo ring closure to the tricyclic products by an electrocyclic reaction. Only in the case of the γ-methylpropargyl ether 13 , the ortho-dienone 11 is further rearranged in low yield to the para-butynylphenol 20 , but the tricyclic ketone 17 is again the main product. New data show that the known thermal cyclisation of aryl propargyl ethers to chromenes (e. g. 4 → 8 ) involves a preliminary [3, 3]-sigmatropic rearrangement.     

Cationic polymerization of α,β-disubstituted olefins. XV. Stereospecific polymerization of butenyl ethers by cationic catalysts

Methyl, ethyl, and isopropyl butenyl ethers, CH₃CH₂CH?CHOR, were polymerized with homogeneous catalysts at ?78°C. Toluene, methylene chloride, and nitroethane were used as solvents, and BF₃O(C₂H₅)₂ and SnCl₄·CCl₃CO₂H were used as catalysts. The stereoregularity of the polymers were compared by x-ray diagrams and infrared absorption ratios. The stereoregularity of polymers increased with increasing content of the trans isomer in the monomer and with increasing polarity of the solvent. In the polymerization of methyl and ethyl butenyl ethers, crystalline polymers were obtained from both the trans and cis isomers. The crystalline polymer prepared from the trans isomer and that from the cis isomer had the same steric structure. This behavior is quite different from that observed in the polymerization of propenyl ethers. It is concluded that the bulkiness of the group on the olefinic β-carbon plays an important role in the stereospecific polymerization of α,β-disubstituted olefins.     

Lanthanoidkomplexe von 1‐(2‐Propenyl)‐ und 1‐(3‐Butenyl)‐1,4,7,10‐tetraazacyclododecan‐4,7,10‐triessigsäure

η³‐1,4,7,10‐tetraazacyclododecane molybdenum tricarbonyl reacts with allyl bromide and 3‐butenyl bromide in dimethylformamide in the presence of K₂CO₃ yielding 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane ( 1a ) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane ( 1b ), which on their part react with bromoacetic acid tert‐butyl ester in CH₃CN to give 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid tert‐butyl ester ( 2a ) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid tert‐butyl ester ( 2b ), respectively. Compounds 2a and 2b are converted into the corresponding acids 1‐(2‐propenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid ( 4a ) (MPC) and 1‐(3‐butenyl)‐1,4,7,10‐tetraazacyclododecane‐4,7,10‐tris‐acetic acid ( 4b ) (MBC) via the trifluoroacetates 3a and 3b . Sm(NO₃)₃(H₂O)₆, LuCl₃(THF)₃, and TmCl₃(H₂O)₆ react with 4a and 4b forming the lanthanide complexes Sm(MPC) ( 5 ), Lu(MPC) ( 6 ), Tm(MPC) ( 7a ) and Tm(MBC) ( 7b ). The IR as well as the ¹H and ¹³C NMR spectra of the new compounds are reported and discussed.