1- ethene, reaction with dimethyl

It should be noted that addition of the tributyltin radical to 1-fluoro-1-(phenylsulfonyl)ethene provides phenyl vinyl sulfone as the only isolated product. However, 2-trimethylsilyl-1-fluoro-1-(phenylsulfonyl)ethene reacts with tributyltin hydride in the presence of AIBN to provide (E)-2-trimethylsilyl-1-fluoro-1-tributylvinylstannane. The vinylstannane is an equivalent for the synthon "H2C=CF " providing a convenient route to 2-fluoro-1-alkenes.8 The trimethylsilyl group can be removed with potassium fluoride in dimethyl sulfoxide-water or oxalic acid-methanol at the end of the reaction sequence. 

The reactive 2/f,5//-benzo[l,2-6 4,5-6 ]bisthiete (81) reacts readily in toluene at 90°C with (E)-1,2-bis(4-hexyloxyphenyl)ethene, dimethyl fumarate, or diethyl maleate to furnish the compounds (82 R = 4-hexyloxyphenyl, C02Me, and C02Et). Reaction with DMAD yields the tetraester derivative (83) <94AG(E)465>. 

Silene Reactions with Organic Dienes. The second example of reactions wdll concern Diels-Alder reactions of silenes. Certainly, as was already mentioned, the diene additions to silaethenes occur much faster than those to ethenes. Over and above that, in most eases other reactions operate in addition. As is shown in Scheme 10, the [4+4] cycloaddition of silaetiienes with 2,3-dimethyl-l,3-butadiene (DMB) leads - independently of tiie direction of silaethene addition to DMB - to one and the same [4+2]... 

Photochemical decomposition of diazo(trimethylsilyl)methane (1) in the presence of alkenes has not been thoroughly investigated (see Houben-Weyl Vol. E19b, p 1415). The available experimental data [trimethylsilylcyclopropane (17% yield) and la,2a,3j8-2,3-dimethyl-l-trimethylsilylcyclopropane (23% yield)] indicate that cyclopropanation occurs only in low yield with ethene and ( )-but-2-ene. In both cases the formal carbene dimer is the main product. In reactions with other alkenes, such as 2,3-dimethylbut-2-ene, tetrafluoroethene or hexafluoro-propene, no cyclopropanes could be detected.The transition-metal-catalyzed decomposition of diazo(trimethylsilyl)methane (1) has been applied to the synthesis of many different silicon-substituted cyclopropanes (see Table 3 and Houben-Weyl Vol.E19b, p 1415) 3.20a,b,2i.25 ( iQp. per(I) chloride has been most commonly used for carbene transfer to ethyl-substituted alkenes, cycloalkenes, styrene, and related arylalkenes. For the cyclopropanation of acyl-substituted alkenes, palladium(II) chloride is the catalyst of choice, while palladium(II) acetate was less efficient, and copper(I) chloride, copper(II) sulfate and rhodium(II) acetate dimer were totally unproductive. The cyclopropanation of ( )-but-2-ene represents a unique... 

Reduction of chlorodifluoromethylketones (32) with tetrakis(N,N-dimethyl-amino)ethene (35) produced carbanion (33) via two-electron reduction, which underwent aldol reaction with aldehydes to form 34 [28]. On the other hand, one-electron reduction of 32 with thiolates produced 36 via radical 35 [29] (Scheme 2.41). 

METHYL-l-PHENYL-ETHENE (98-83-9) Forms explosive mixture with air (flash point 129°F/54°C). Violent reaction with strong oxidizers, butyl lithium, oleum, xenon tetra-fluoride. Unless inhibited, forms unstable peroxides. Incompatible with acids. Reacts with heat and/or lack of appropriate inhibitor concentration, and/or contact with catalysts for vinyl or ionic polymerization, such as aluminum, iron chloride, or 2,5-dimethyl-2,5-di(rert-butylperoxy)hexane. The uninhibited monomer vapor may block vents and confined spaces by forming a solid polymer material. 

As can be seen in the intramolecular cycloaddition (Section 8.03.5.1), the intermolecular Diels-Alder reactions between functionalized 2(l/f)-pyrazinones 83 and dimethyl acetylenedicarboxylate (DMAD) forming bicyclo adducts 84 has been shown to be significantly rate enhanced and increased in yields by using controlled microwave irradiation compared to the conventional thermal protocols (Scheme 21) <2002JOC7904>. The microwave-assisted Diels-Alder reactions of substituted 2(l//)-pyrazinones with ethene are significantly more effective utilizing prepressurized (up to 10 bar) reaction vessels <20040BC154>. 

These results are supported by those from the reaction of (Z)-l-(ethylsulfmyl)-2-(ethyl-thio)ethene with iodomethane or dimethyl disulfide. 

Photocycloadditions of naphthalene derivatives to alkcnes have been recently reviewed.60 Examples of such reactions are the photocycloaddition of naphthalene to 2,3-dihy-drofuran,61 of 4-methoxy-l-naphthonitrile to acrylonitrile62 and of 2-trimethylsiloxynaph-thalene to methyl acrylate.63 2-Naphthols undergo cycloaddition with ethene in the presence of aluminum trihalides only.64 Other bicyclic aromatic compounds, e.g. A-acylindoles65-67 and /V-methylphenanthrene-9,10-dicarboximide,68 have also been studied in detail. Irradiation of 5/f-dibenzo[u,i7]cyclohepten-5-one (21) and dimethyl 2-methylfumarate (22) in dioxane gives the cyclobutane adduct 23 in 73% yield.69... 

Experimentally, the kinetic data obtained from the pyrolysis of cyclobutane to ethene between 696 and 1007"C using a very low-pressure pyrolysis technique is consistent with a 1,4-diradical reaction route.82 A diradical process is also favored over a concerted pathway for the formation of nearly 1 1 mixtures of cis- and tranj-but-2-enes and [l,2-2H2]ethene from the thermal rupture of cb-l,2-dimethyl[cw,firn /-3,4-2H2]cyclobutane (5),83... 

Obtained from active methylene compounds, such as malonic esters, -0x0 esters and jS-oxo sulfones, iodonium ylides serve as precursors of the corresponding carbenes. Their decomposition by a catalytic amount of a copper salt in the presence of a C-C double bond has been used for inter- and intramolecular cyclopropanation reactions. Thus, reaction of cyclohexene with bis(methoxycarbonyl)methylene(phenyl)iodine(III) under the catalytic action of bis(acetylacetonato)copper(II) yielded dimethyl bicyclo[4.1.0]heptane-7,7-dicarboxylate (1) (38%, mp 91-93°C) in addition to tetrakis(methoxycarbonyl)ethene (41%). ... 

Various alkylcyclopropanes have been converted to (l-alkenyl)cyclopropanes by dehydrogenation with trimethylsilyl triflate, selenium dioxide,tetrachloro-1,4-benzoquinone, 2,3-dichloro-5,6-dicyano-l,4-benzoquinone, di-/er/-butyl dicarbonate and potassium tert-butoxide/dimethyl sulfoxide. A related transformation is the Ramberg-Back-lund reaction of bis(l-trimethylsilylcyclopropylmethyl) sulfone which gave ( )-l,2-bis(l-trimethylsilylcyclopropyl)ethene in fair yield. ... 

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