4- alkyl-2-vinyl

Robinson Annulation Sequential Michael addition/aldol condensation between a ketone enolate and an alkyl vinyl ketone (i.e. MVK) to give a cyclohex-2-en-l-one... 

The addition proceeds in three discrete steps and the intermediates can be isolated. Simple alkenes are less reactive than alkynes and do not undergo the addition to aHylic boranes, but electron-rich alkyl vinyl ethers react at moderate temperatures to give 1,4-dienes or dienyl alcohols (440). 

When using a cation source in conjunction with a Friedel-Crafts acid the concentration of growing centers is most often difficult to measure and remains unknown. By the use of stable carbocation salts (for instance trityl and tropyhum hexachloroantimonate) the uncertainty of the concentration of initiating cations is eliminated. Due to the highly reproducible rates, stable carbocation salts have been used in kinetic studies. Their use, however, is limited to cationicaHy fairly reactive monomers (eg, A/-vinylcarbazole, -methoxystyrene, alkyl vinyl ethers) since they are too stable and therefore ineffective initiators of less reactive monomers, such as isobutylene, styrene, and dienes. 

Cationic Polymerization. For decades cationic polymerization has been used commercially to polymerize isobutylene and alkyl vinyl ethers, which do not respond to free-radical or anionic addition (see Elastomers, synthetic-BUTYLRUBBEr). More recently, development has led to the point where living cationic chains can be made, with many of the advantages described above for anionic polymerization (27,28). 

Fig. 1. Effect of ion pairing on stereochemistry of propagation for alkyl vinyl ethers, where L is large substituent S, small substituent.

As shown in Table 3, the glass-transition temperatures of the amorphous straight-chain alkyl vinyl ether homopolymers decrease with increasing length of the side chain. Also, the melting points of the semicrystalline poly(alkyl vinyl ether)s increase with increasing side-chain branching. 

Poly(alkyl vinyl ether) CAS Registry Number T/C Mp, °C... 

The refined grade s fastest growing use is as a commercial extraction solvent and reaction medium. Other uses are as a solvent for radical-free copolymerization of maleic anhydride and an alkyl vinyl ether, and as a solvent for the polymerization of butadiene and isoprene usiag lithium alkyls as catalyst. Other laboratory appHcations include use as a solvent for Grignard reagents, and also for phase-transfer catalysts. 

Pyrazolin-5-ones with an exocyclic double bond at the 4-position (369 X = CMe2> react as heterodienes towards alkyl vinyl ethers (77G91). The kinetics of this Diels-Alder reaction giving pyrazolopyrans (370) have been studied. 

Typical of these materials are the poly(vinyl thioethers), the poly(vinyl isocyanates), the poly(vinyl ureas) and the poly(alkyl vinyl ketones). Methyl isopropenyl ketone and certain vinylpyridine derivatives have been copolymerised with butadiene to give special purpose rubbers. 

A free-radical reaction is a chemical process which involves molecules having unpaired electrons. The radical species could be a starting compound or a product, but the most common cases are reactions that involve radicals as intermediates. Most of the reactions discussed to this point have been heterolytic processes involving polar intermediates and/or transition states in which all electrons remained paired throughout the course of the reaction. In radical reactions, homolytic bond cleavages occur. The generalized reactions shown below illustrate the formation of alkyl, vinyl, and aryl free radicals by hypothetical homolytic processes. 

The reactivity of a series of hydrocarbons toward oxygen measured under a standard set of conditions can give some indication of the susceptibility of various structural units to autoxidation. Table 12.10 gives the results for a series of hydrocarbons. These data indicate the activating effect of alkyl, vinyl, and phenyl substituents. 

In 1950, Dahlquist et al. [82] reported the use of polyvinyl A -alkyl carbamates as PSA release materials. Since then, many other types of alkyl side chain polymers have been patented for use as release coatings, including copolymers based on higher alkyl acrylates or methaci ylates [83-86], polyvinyl esters of higher aliphatic fatty acids [87], higher alkyl vinyl esters or ethers and a maleic... 

A. number of rutro compounds used m ndturdl product synthesis have been prepared by the n of alkyl halides Some recent examples are summarized m Table 2 4 fi-Nitro carbonyl compounds are important for synthesis of natural products The reaction of alkyl vinyl ketones with sodium nitrite and acetic acid in THF gives thecorrespondmgfi-nitro carbonyl compounds in42-82% ""rhis method is better for the preparation of fi-nitro carbonyl compounds than the nitration of the corresponclmg halides... 

Figure 8.5 A comparison of alkyl, vinylic, and acetylide anions. The acetylide anion, with sp hybridization, has more s character and is more stable. Electrostatic potential maps show that placing the negative charge closer to the carbon nucleus makes carbon appear less negative (red).

Strategy Identify the distinct carbons in the molecule, and note whether each is alkyl, vinylic, aromatic, or in a carbonyl group. Then predict where each absorbs, using Figure 13.7 as necessary. 

However, the configuration of the major isomer obtained in the conjugate addition to methyl ( )-3-[(35,)-3-tot-butoxycarbonyl-2,2-dimcthyl-4-oxazolidinyl]-2-propenoate (entry 3) did not depend on the cuprate type alkyl-, vinyl-, 2-methylpropenyl-, phenyl-, and benzvl-cuprates induced the same sense of asymmetry, although the absolute configuration was not determined5. Here also, the stereochemical outcome was not dependent upon the geometry of the double bond. 

The rate of oxidation/reduction of radicals is strongly dependent on radical structure. Transition metal reductants (e.g. TiMt) show selectivity for electrophilic radicals (e.g. those derived by tail addition to acrylic monomers or alkyl vinyl ketones - Scheme 3.89) >7y while oxidants (CuM, Fe,M) show selectivity for nucleophilic radicals (e.g. those derived from addition to S - Scheme 3,90).18 A consequence of this specificity is that the various products from the reaction of an initiating radical with monomers will not all be trapped with equal efficiency and complex mixtures can arise. 

While there is clear evidence for complex formation between certain electron donor and electron acceptor monomers, the evidence for participation of such complexes in copolymerization is often less compelling. One of the most studied systems is S-.V1 Al I copolymerization/8 75 However, the models have been applied to many copolymerizations of donor-acceptor pairs. Acceptor monomers have substituents such as carboxy, anhydride, ester, amide, imide or nitrile on the double bond. Donor monomers have substituents such as alkyl, vinyl, aryl, ether, sulfide and silane. A partial list of donor and acceptor monomers is provided in Table 7.6.65.-... 

For the synthesis of quinolines and isoquinolines the classical approaches are the Skraup and the Bischler-Napieralski reactions. The reaction of substituted anilines with different carbonyl compounds in acid medium has been reported to be accelerated under microwave irradiation to give differently substituted quinolines and dihydro quinolines [137]. Although the yields are much better and the conditions are milder than under conventional heating, the acidity of the medium may prevent the preparation of acid-sensitive compounds. Thus, alternative approaches have been investigated. Substituted anilines and alkyl vinyl ketones reacted under microwave irradiation on the surface of sihca gel doped with InCU without solvent [137] to furnish good yields of quinohnes 213 (Scheme 77). 

Lithium dialkylcopper reagents can be oxidized to symmetrical dimers by O2 at -78°C in THF. The reaction is successful for R = primary and secondary alkyl, vinylic, or aryl. Other oxidizing agents (e.g., nitrobenzene) can be used instead of O2. Vinylic copper reagents dimerize on treatment with oxygen, or simply on standing at 0°C for several days or at 25°C for several hours, to yield LS-dienes." ... 

Catalytic hydrogenation with platinum liberates the hydrocarbon from methylcobalamin (57) and from alkyl-Co-DMG complexes (161), but not from pentacyanides with primary alkyl, vinyl, or benzyl ligands, though the cr-allyl complex yields propylene (109). Sodium sand gives mixtures of hydrocarbons with the alkyl-Co-salen complexes (64). Dithioerythritol will liberate methane from a variety of methyl complexes [cobalamin, DMG, DMG-BF2, G, DPG, CHD, salen, and (DO)(DOH)pn] (156), as will 1,4-butanedithiol from the DMG complex (157), and certain unspecified thiols will reduce DMG complexes with substituted alkyl ligands (e.g., C0-CH2COOH ->CH3C00H) (163, 164). Reaction with thiols can also lead to the formation of thioethers (see Section C,3). 

Synthesis of Phosphonic and Phosphinlc Acids and their Derivatives.-The phosphonium adducts from PCl and alkyl vinyl ethers are converted into the corresponding phosphonic dichlorides by hexamethyldisiloxane. Oxidative phosphorylation of the 1,3-butadienes (53) affords the phosphonic dichlorides (54). 

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