Bis- -alkene

Aus Epoxiden werden durch dasselbe Reduktionspaar bzw. durch Wolfram(VI)-chlo-rid/Lithiumjodid Alkene bis zu 75-98% d.Th. erhalten1 ... 

Potassium nitrosodisulfonate, 258 Trimethylsilyl chlorochromate, 327 By hydrolysis of acetals or thioacetals Amberlyst ion-exchange resin, 152 Methylthiomethyl p-tolyl sulfone, 192 By isomerization of allylic alcohols N-Lithioethylenediamine, 157 By oxidation of aromatic side chains Trimethylsilyl chlorochromate, 327 From oxidative cleavage of alkenes [Bis(salicylidene-7-iminopropyl)-methylamine]cobalt(II)... 

Wood flour from maple, 120 mesh, vacuum dried. The coupling agent was maleated polyethylene containing 1% (w/w) grafted maleic anhydride (Epolene G-2608, Eastman Chemicals). The lubricant was alkene bis fatty amid (Glycolube WP-2002, Lonza Inc.) [4]. 

The novel nitrenium ion-mediated alkene bis-functionalization used by Bowen and Wardrop in their synthesis of swainsonine (cf Scheme 76 Section 3.5.2) also featured in their total synthesis of (-f)-castanospermine (654) (Scheme 90). The derivatized xylopyranoside (+)-681, prepared in four steps fixrm D-xylose, was converted in stepwise fashion into lactone (—)-682 by rearrangement of the allyl ether to the corresponding enol ether, hydrolysis to a mixture of lactol anomers, and oxidation. Carefijl methano-lysis in the presence of camphorsulfonic acid and adjustment of the pH to 7... 

Silylzinc reagents are also employed for the silylmetalation reaction of alkynes and alkenes. Bis(dimethylphenylsilyl)zinc adds across these unsaturated substrates in the presence of a copper(I) catalyst (Scheme 3-34). The addition reaction proceeds in a stereospecific manner always cis adducts are produced. 

If alkyl groups are attached to the ylide carbon atom, cis-olefins are formed at low temperatures with stereoselectivity up to 98Vo. Sodium bis(trimethylsilyl)amide is a recommended base for this purpose. Electron withdrawing groups at the ylide carbon atom give rise to trans-stereoselectivity. If the carbon atom is connected with a polyene, mixtures of cis- and rrans-alkenes are formed. The trans-olefin is also stereoseiectively produced when phosphonate diester a-carbanions are used, because the elimination of a phosphate ester anion is slow (W.S. Wadsworth, 1977). 

The cyclohexadiene derivative 130 was obtained by the co-cyclization of DMAD with strained alkenes such as norbornene catalyzed by 75[63], However, the linear 2 1 adduct 131 of an alkene and DMAD was obtained selectively using bis(maleic anhydride)(norbornene)palladium (124)[64] as a cat-alyst[65], A similar reaction of allyl alcohol with DMAD is catalyzed by the catalyst 123 to give the linear adducts 132 and 133[66], Reaction of a vinyl ether with DMAD gives the cyclopentene derivatives 134 and 135 as 2 I adducts, and a cyclooctadiene derivative, although the selectivity is not high[67]. 

Diaryl disulfides and diselenides add to alkynes to afford the (Z)-l, 2-bis(ar-ylthio)alkenes 193 and (Z)-l,2-bis(arylseleno)alkenes 194. Under CO pressure, carbonylative addition takes place to give thio esters and the selenoketones 195[I07], The selenoketones are converted into the /J-seleno-a, 3-unsaturated aldehydes 196 by Pd-catalyzed hydrogenolysis with HSnBu3[108,109],... 

Methylarsine, trifluoromethylarsine, and bis(trifluoromethyl)arsine [371-74-4] C2HAsF, are gases at room temperature all other primary and secondary arsines are liquids or solids. These compounds are extremely sensitive to oxygen, and ia some cases are spontaneously inflammable ia air (45). They readily undergo addition reactions with alkenes (51), alkynes (52), aldehydes (qv) (53), ketones (qv) (54), isocyanates (55), and a2o compounds (56). They also react with diborane (43) and a variety of other Lewis acids. Alkyl haUdes react with primary and secondary arsiaes to yield quaternary arsenic compounds (57). 

A newer method for the preparation of nitronic esters, namely utilizing the (9-trimethyl-silyl ester, has been reported and these are prepared by the reaction of alkylnitro compounds and (V,(V-bis(trimethylsilyl)acetamide. These nitronic esters also undergo cycloaddition with alkenes to produce isoxazolidines (equation 54) (74MIP41601, 74DOK109, 78ACS(B)ll8). 

Diene moieties, reactive in [2 + 4] additions, can be formed from benzazetines by ring opening to azaxylylenes (Section 5.09.4.2.3). 3,4-Bis(trifluoromethyl)-l,2-dithietene is in equilibrium with hexafluorobutane-2,3-dithione, which adds alkenes to form 2,3-bis-(trifluoromethyl)-l,4-dithiins (Scheme 17 Section 5.15.2.4.6). Systems with more than two conjugated double bonds can react by [6ir + 2ir] processes, which in azepines can compete with the [47t + 27t] reaction (Scheme 18 Section 5.16.3.8.1). Oxepins prefer to react as 47t components, through their oxanorcaradiene isomer, in which the 47r-system is nearly planar (Section 5.17.2.2.5). Thiepins behave similarly (Section 5.17.2.4.4). Nonaromatic heteronins also react in orbital symmetry-controlled [4 + 2] and [8 + 2] cycloadditions (Scheme 19 Section 5.20.3.2.2). 

Intramolecular alkylnitrene addition to an alkenic moiety situated S,e to the electron deficient center has been utilized for the preparation of bi- and tri-cyclic aziridines (Scheme 11) (68JA1650). Oxidation of the primary alkylamine can be effected cleanly with NCS, LTA or mercury(II) oxide. 

Fluorobenzene is readily alkylated with alkenes in the presence of protic acids, however, the isomenc purity of the product is poor, and polysubstitution can result Thus, propene and sulfuric acid alkylate fluorobenzene at 20 C to yield a 45 55 ortho/para ratio of the inonoalkyl product m addition to di- and triiso propylfluorobenzene [i5] The reaction of benzene and trifluoropropene at 25 °C in HF-BF3 gives a mixture of mono-, bis-, and tns(3,3,3-trifluoropropyl)ben zene [72, 75] (equation 12)... 

Table 21. l,l-Bis(trifluoroinethyl)alkenes Prepared from Hexafluoroisopropylidenetriphenylphosphorane [5[Pg.590]

The scope of haloaliphatic additions to alkenes has been extended to the preparation of 1,2-bis(perfluoroalkyl)iodoethanes by the addition of perfluoroalkyl iodides tofluoroalkyl alkenes [73] (equation 12) or to alkadienes [14] (equation 13)... 

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