Allyl halides photochemical

Allyldiethylamine behaves similarly, but the yields are low since neither the starting amine nor the products are stable to the reaction conditions. For the efficiency of the cyclopropanation of the allylic systems under discussion, a comparison can be made between the triplet-sensitized photochemical reaction and the process carried out in the presence of copper or rhodium catalysts whereas with allyl halides and allyl ethers, the transition metal catalyzed reaction often produces higher yields (especially if tetraacetatodirhodium is used), the photochemical variant is the method of choice for allyl sulfides. The catalysts react with allyl sulfides (and with allyl selenides and allylamines, for that matter) exclusively via the ylide pathway (see Section 1.2.1.2.4.2.6.3.3. and Houben-Weyl, Vol. E19b, pll30). It should also be noted that the purely thermal decomposition of dimethyl diazomalonate in allyl sulfides produces no cyclopropane, but only the ylide-derived product in high yield.Very few cyclopropanes have been synthesized by photolysis of other diazocarbonyl compounds than a-diazo esters and a-diazo ketones, although this should not be impossible in several cases (e.g. a-diazo aldehydes, a-diazocarboxamides). Irradiation of a-diazo-a-(4-nitrophenyl)acetic acid in a mixture of 2-methylbut-2-ene and methanol gave mainly l-(4-nitrophenyl)-2,2,3-trimethylcyclo-propane-1-carboxylic acid (19, 71%) in addition to some O-H insertion product (10%). ... 

In addition to cation intermediates, radical intermediates can be used to introduce bromine or chlorine into a molecule. Both allylic and benzylic moieties form resonance stabilized free radicals that react with bromine or chlorine to give the corresponding halide. Allylic radicals are easily accessible from the corresponding allylic halides, particularly allyl iodides (secs. 13.3-13.5). Benzylic radicals are available from benzylic halides and also directly from the hydrocarbon, if it bears a benzylic hydrogen. Addition of bromine to 167 (in the presence benzoyl peroxide and photochemical initiation) gave benzylic bromide 168 in high... 

The (T-allyl complexes may be prepared by reactions of anionic metal carbonyl complexes with allyl halides. These a compounds subsequently rearrange to 7r-allyl complexes by thermal or photochemical reactions. 

Other Metals.—Photochemical or thermal displacement of CO from (ij -allyl)Mn(CO)4 with PX3 (X=R or OR) yields ( -allyl)Mn(CO)2(PX3)2 and (rj3.allyl)Mn(CO)(PX 3) 3 complexes. N.m.r. studies of the latter at low temperature indicate a pseudo-octahedral geometry with rram-phosphorus atoms. C studies of ( -allyl)Mn(CO)4 have also been reported, but quadrupole relaxation by the Mn prohibits any determination of the mechanism of fluxionality. Reaction of [V(CO)4L2] with allyl halides yields ( -allyl)V(CO)3L2 complexes (La = diars or arphos). Similar ( j -methylallyl)V(CO)3L2 complexes (La=arphos or dppm) may be prepared by reaction of isoprene with HV(CO)4La isomers with methyl groups in different positions are obtained. Reaction of CpaTaCla with RMgCl yields Cp2Ta(H)(olefin) complexes (olefin=propene, but-l-ene, pent-l-ene, or cyclopentene). The olefin is easily displaced by phosphine, and the complexes react with Ha to give CpaTaHs. ... 

Allylic silanes react with aldehydes, in the presence of Lewis acids, to give an allyl-substituted alcohol. In the case of benzylic silanes, this addition reaction has been induced with Mg(C104)2 under photochemical conditions. The addition of chiral additives leads to the alcohol with good asymmetric induction. In a related reaction, allylic silanes react with acyl halides to produce the corresponding carbonyl derivative. The reaction of phenyl chloroformate, trimethylallylsilane, and AICI3, for example, gave phenyl but-3-enoate. ... 

A number of allylic chlorides have been reported to yield photoproducts characteristic of the alkene moiety and not of the C—X bond123. Allyl and crotyl halides undergo photochemical reactions with chromium, molybdenum and tungsten complexes, which involve C—X bond cleavage133. 

The preparation of indoles by the benzyne route is illustrated by the base-induced cyclization of the amino-alcohols (171 R = H or Me) to indole and 3-methylin-dole, respectively/ The photochemical reaction of o-bromo- or o-iodo-aniline with the enolates (172 R = H, Me, or PrO leads to indoles (173)/ The salt (174), generated by the action of lithium di-isopropylamide on o-tolyl isocyanide, serves as a source of diverse indole derivatives (i) it cyclizes spontaneously to 1-lithioindole, which forms 3-alkyl-indoles on treatment with alkyl halides in the presence of magnesium iodide, (ii) it reacts with allyl esters RC02CH2CH=CH2 (R = alkyl or aryl) to give the ketones (175), which cyclize... 

Radical Allylation Reactions. Trimethyl 2-[(tributylstannyl) methyl]-2-propenyl silane reacts with organic halides under photochemical conditions (irradiation with a medium pressure mercury lamp through a pyrex filter) at temperatures below 20 °C to give various allylsilanes (eq 7). The ease of the reaction was found to be halide dependent with those affording more electrophilic radicals generally behaving most effectively. 

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