Methylene substituted

Pure (9-terphenyl can be obtained by fractional distillation. To obtain high purity m- or -terphenyl, the appropriate distillation fraction has to be further purified by recrysta11i2ing, 2one refining, or other refining techniques. Currently, litde demand exists for pure isomers, and only a mixture is routinely produced. Small amounts of acetone, ethanol, or methanol are used to promote dehydrocondensation, and as a result, minor amounts of methyl- or methylene-substituted polyphenyls accompany the biphenyl and terphenyls produced. For most purposes, the level of such products (<1%) is so small that their presence can be ignored. For appHcations requiring removal of these alkyl-polyphenyl impurities, an efficient process for their oxidative destmction has been described (38). 

Treatment of natural rubber with chlorine gives a product, chlorinated rubber, with a maximum chlorine content of 65% corresponding to the empirical formula C10H11CI7. Such a compound corresponds neither to a hypothetical simple addition to the double bond (Figure 30.6 (I)) nor to a product with a-methylenic substitution in addition (II). 

Stansbury and Bailey. A review by Colombam on addition-fragmentation processes is also relevant. Monomers used in ring-opening are typically vinyl (e.g. vinylcyclopropane - Scheme 4.20 Section 4.4.2.1) or methylene substituted cyclic compounds (e.g. ketene acetals - Section 4.4.2.2) where addition to the double bond is followed by p-scission. 

Scheme 3.45, Eq. 2) through the most stabilized zwitterion to give only one stereoisomer of target 5-methylene-substituted nitronate (35 h). 

Like the nitrone-olefin [3 + 2]-cycloaddition, the nitrone-allene [3 + 21-cycloaddition also takes place regioselectively to furnish methylene-substituted isoxazoli-dine derivatives. The substituents of the 3- and 4-positions of the cycloadducts 72a and 72b are disposed cis in contrast, the reaction of 70 with allenyl sulfone 71c gives rise to the trans-cycloadduct 72c exclusively (Table 12.4). On treatment with base or heating, methyleneisoxazolidines 72 readily rearrange to isoxazo-lines via a 1,3-hydrogen shift. 

In some cases, the nature of the electrophile and the type of base used can determine the type of product isolated. For example, after treatment of bis(pyrazol-l-yl)methane (Scheme 34) with ri-BuLi at 25°C, reactive alkyl halides such as methyl iodide or benzyl chloride favor formation of the methylene substituted (kinetic) products, whereas with carbonyl... 

The first ring expansion of a 1,2,4-trioxolane to a 1,2,4-trioxane was observed with (47) where the orientation of the peroxide group was crucial in assisting the triflate to leave (Equation (2)). A 1,2-peroxide shift then follows with loss of silicon giving the methylene substituted 1,2,4-trioxane (48) as the product <91JA8168>. The equatorial triflate does not undergo rearrangement. 

Methylene-substituted tetrahydro-l,3-oxazine 141 underwent ring opening in response to nucleophilic attack by carboxylic acids or thiophenols to afford the A -acetyl derivatives of the corresponding 0-acyl-l,3-amino alcohols 168 or aminoalkyl sulfides 169 in high yields (Scheme 27) <2006JC0262>. 

Both phenylhydrazones and imines derived from 5-halogeno-2-hydroxyacetophenones 510 were cyclized to the corresponding 4-methylene-substituted l,3-benzoxazin-2-ones 194 and 511 on treatment with 0.5 or O.bequiv of triphosgene under mild conditions (Scheme 96) <2003X8163, 2004SC71>. In the similar reactions of arylhydra-zones of 2-hydroxyacetophenones with 1 equiv of triphosgene, spiro-l,3-benzoxazine dimers were formed <2002JCM473>. 

The desUylation strategy has been used for the cycloaddition of the parent thiocarbonyl yhde la with aldehydes and reactive ketones. The product obtained using A-methyl-3-oxoindolinone as the trapping agent corresponds to the spiro-cyclic compound 125 (168). Thioketene (5)-methylide (127) was reported to react with aromatic aldehydes and some ketones to furnish 2-methylene-substituted 1,3-oxathiolanes (128) (51) (Scheme 5.42). 

Alkylidene-phosphapyrazolines 98-101 are much more thermally stable than their relatives 88, which do not possess the exo-methylene substitution. Dediazo-niation of 98 required heating in toluene at 110°C and gave one or more of the following products, probably via intermediate diphenylmethylene(vinylidene)phos-phoranes methylenephosphiranes, (2-siloxyvinyl)phosphanes, 2//-l,3-oxaphos-pholes, and l-alkylidene-2,3-dihydro-l//-benzo[c]phospholes (169). Thermolysis of 100 ( R = t-Bu, 1-adamantyl) afforded isolable 2-phosphabutadienes (169). The photochemical elimination of N2 from 98 generated cyclic azomethine imine dipoles 104 (Scheme 8.24), which rearrange to compounds 105 and 106 that could be further trapped with DMAD to form 107 (170). 

Especially high efficiency (93%) was found when copolymer containing 60 mol% of styrene units was used. The efficiency was in this case much higher than obtained for polymerization of homopolymer-type prepolymer, both types - methylene substituted and unsubstituted. Improvement of solubility of the newborn polymer by the methyl substituent allowed to analyze the product by GPC method. It was found that molecular weight of the newborn polymer was lower then molecular weight of template polymer. It was the evidence that the newborn polymer is not connected with the template. 

Phosgene acts as an acylating agent to give methylene-substituted l,3-dithietan-2-ones (66AG(E)970, 79LA1715). 

Heterocyclization of a-mercapto acids with (azolylimino)indolones 182 (Scheme 36) afforded the spirocyclic thiadiazepinones 183 <1989IJB639, 1994PS27>. gem-Dithiol addition to bis(methylene)-substituted diketopiper-azine 168 afforded the bridged bicyclic structure 169 featuring two dithiazepane rings (Scheme 33) <1981JHC1545>. 

Methylene substituted diamantanes are also obtained in a manner analogous to that employed for adamantane. Treatment of diamantane with concentrated sulfuric acid gives good yields of diamantanone 26S). 

The reported 2731 yield of adamantanone oxime from this reaction (63 %) is misleading since it is based on Cl2 as the limiting reagent. Careful product analyses have shown that the overall ratio of tertiary to secondary substitution products ( 2) is quite normal275), While this reaction is clearly much less useful for the preparation of methylene substituted adamantanes than the ionic processes discussed above, it may be applicable in more specialized cases such as, for example, the synthesis of polyalkylsubstituted adamantanones where the ionic processes work poorly. 

While the preparation of bridgehead (mono-,di-, etc.) and methylene substituted adamantanes is extremely easy, polysubstituted adamantanes in which one of the substituents is at a methylene position are much less readily prepared. In general, special techniques must be developed for each specific substitution pattern. 

The chemistry of methylene-substituted 2-oxetanones, and in particular diketene, has attracted a vast amount of research over the years, so other alkylene-substituted oxetanes and oxetan-2-ones, including methylene oxetanes, are discussed separately in Section 2.05.7.4. Diketene is also known as 4-methylene-2-oxetanone and a notable difference between this and other 2-oxetanones is that it undergoes thermal decomposition by a cycloreversion reaction to give ketene, rather than forming allene and C02. CHEC-II(1996) refers to a series of comprehensive reviews of the chemistry of this compound <1996CHEC-II(1)721>. 

A heterobimetallic polycarbostannane 64142 was obtained from the reaction of the bidentate [Fe(CO)2Cp-X-Cp(CO)2Fe]2- (X = -CHNMe2CHNMe2-) with Ph2SnCl2. The molecular weight as determined by osmometry was Mn = 8.5 x 1()3 gmol-1, indicating relatively short chains. The reaction of the methylene-substituted dianionic... 

Collman18 described numerous ligand reaction methods for preparing methylene-substituted 0-diketone complexes. Often these materials cannot be prepared by other techniques because of the lack of stability either of the ligand or its alkali metal salt. A particularly useful procedure leading to the introduction of a functionally active substituent has been reported.14... 

Methylene-substituted 2-oxetanones, and in particular diketene, have attracted a vast amount of work Schemes 49... 

With 1-phenylsulfinylallene, the residual double bond is found mainly at the 5-position in the cycloadduct (85SC663), whereas nitrogen-substituted allenes afford mainly 4-methylene-substituted isoxazolines [90JCS(P1)533 91JCS(P1)1843]. The regioselectivity of addition to 1-fluoro- and 1,1-difluoro-allene depends on the nitrile oxide and is thought to reflect the... 

High diastereoselectivity is found in the reaction of the racemic exo-methylene substituted 3-azabicyclo[3.3.0]octane 4 with bis(AM-toluencsulfonyl)sulfodiimide52. The tosylamide 5 is obtained in 81 % yield. 

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