Ring opening cyclic

Grubbs found that (4 a) ring-opened cyclic olefins, and then react with an acrylate to produce end functionalized linear olefins, giving a ring-opened cross metathesis product (ROCM) with two olefins with differing reactivity (equation 19). Key to the distribution of products was the relative rates of ring-opening and cross metathesis with the functionalized olefin. 

J. Kuroda,T. Fukai, and T. Nomura, Colhsion-induced dissociation of ring-opened cyclic depsipeptides with a guanidino group by electrospray ionization/ion trap mass spectrometry, J. Mass Spectrom. 36 (2001), 30-37. 

The solid-state polymerization of the following classes of monomers is discussed diacetylenes, monoacetylenes, mono- and dienes, ring-opening cyclic monomers, and transition metal systems. With particular emphasis on open questions and current problems, the chemiced, structural, and physical properties of the resultant polymers are sununarized. A brief prognosis is offered. 

Silver perchlorate Ring expansion of isocyclics by 1,1-dihalogenocyclopropane ring opening Cyclic 2 -alkoxy-a,) -ethylenehalides... 

Cyclic compounds capable of undergoing ring opening (alkylene oxides, lactones, lactams, anhydrides, etc.). 

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. 

Cyclic ether and acetal polymerizations are also important commercially. Polymerization of tetrahydrofuran is used to produce polyether diol, and polyoxymethylene, an excellent engineering plastic, is obtained by the ring-opening polymerization of trioxane with a small amount of cycHc ether or acetal comonomer to prevent depolymerization (see Acetal resins Polyethers, tetrahydrofuran). 

Cyclic aryl ether ketones have been prepared from l,2-bis(4- uoroben2oyl)ben2ene and bisphenols under pseudo high dilution conditions. These materials undergo ring-opening polymeri2ation in the presence of an anionic catalyst (87). 

Ring-opening reactions are best known in the pyridazine ring. For example, the N-aryl cyclic hydrazides (321) undergo ring opening with alkali to give the N-aminoimides (322),... 

A -Pyrazolines and A -isoxazolines (302 Z = NH, O) are cyclic hydrazones and oximes, respectively. 2-Pyrazolines are quaternized at the 2-position (306 307) (64AHC(. ll). 1,3,4-Oxadiazolines (e.g. 308) are very easily ring-opened (66AHCi7 183). 

WASSERMANN BORMANN Maciocydiclactamsynttwsis Ring expansion sequence of lactams by reaction with cyclic Iminoethers followed by reductive ring opening to a macrocyclic lactam. 

The bis(silyloxy)cyclobutenes are also subject to a variety of special reactions. Probably the most interesting is the observation that they readily undergo a ring-opening reaction leading to a butadiene derivative. This reaction has already been used to prepare large-ring diketones from cyclic 1,2-diesters. 

In recent years there has been some interest in the ring-opening polymerisation of cyclic trimers using a weak base such as lithium silanolate which gives high molecular weight products of narrow molecular weight distribution free of cyclic materials other than the unreacted trimer. 

With cyclic ketones, the a-cleavage can also be followed by intramolecular bydn en abstraction that leads eventually to an unsaturated ring-opened aldehyde ... 

The addition of nucleophiles to cyclic fluoroolefins has been reviewed by Park et al. [2 ]. The reaction with alcohols proceeds by addition-elimination to yield the cyclic vinylic ether, as illustrated by tlie reaction of l,2-dichloro-3,3-di-fluorocyclopropene Further reaction results in cyclopropane ring opening at the bond opposite the difluoromethylene carbon to give preferentially the methyl and ortho esters of (Z)-3-chloro-2-fluoroacrylic acid and a small amount of dimethyl malonate [29] (equation 8). 

The cation [NSO(NPCl2)2] (14.11) is the proposed intermediate in this ring-opening polymerization process. This cation is extremely reactive, as illustrated by the isolation of the solvent-derived product 14.12 when it is generated by halide abstraction from the cyclic precursor with AICI3 in l,2-dichloroethane. °... 

Five- (70, = 1) and six-membered (70, n = 2) enamines substituted in position 2 generally exist in the cyclic form. Lukes and co-workers observed that partial ring-opening occurs with the pyrroline 157) or piperideine 163,164) derivatives by atmospheric moisture. This leads to the formation... 

Occasionally it happens that the oxo compound, produced by oxidation, forms a hydrate which is further oxidized to a dihydroxy compound. Attention must be given to the possibility (so far unreported) that when the hydrated species is in equilibrium with a trace of the ring-opened structure a sufficiently fast oxidation rate of the amino-aldehyde (i.e. the acyclic structure) could lead to the incorrect conclusion that the original material was not cyclic. 

Usually, the cychc isomers 272 are preferred in the sohd state. X-Ray structural evidence was obtained for compound 272 [R = COPh, R = Me, R = R" = H, R = CF3 X = O (92KK1184)]. In solution, the cyclic and ring-opened isomers are found in equihbria in ratios depending on polarity of the solvent and structural factors (see 88KGS3 95ZOB705 96AHC(66)1 for reviews). 

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