Inducing reaction

Lee Y-Y, Leone S R, Champkin P, Kaltoyannis N and Price S D 1997 Laser photofragmentation and coiiision-induced reactions of sit and siH - Chem. Phys. 106 7981-94... 

D. McGinniss, in Ultraviolet Eight Induced Reactions in Polymers (Sympos. Ser. No. 25), American Chemical Society, Washington, D.C., 1976. 

Contamination of blood products with lymphocytes can lead to transfusion-induced reactions ranging from a mild fever to severe reactions such as alloimmunization and graft versus host disease (GvHD), in which the transfused lymphocytes (graft) survive the defensive immune reaction of the patient (host) and start a reaction which destroys the cells of the host. The patient also may develop an immune response to the human leukocyte antigen (HLA) type of the graft s cells and reject all platelet transfusions that do not match their own HLA system. The HLA system, found on blood platelets and lymphocytes, is more compHcated than, but similar to, the ABO blood group system of red cells. 

From the colorless state it can be switched with light of short wavelength (A = 380 nm) via an electrocycHc ring opening and cis/trans rotation of one half of the molecule into a state with violet/purple color. The reverse reaction is effected by visible light (A = 580 nm). Since the system is metastable, one of the two reaction directions is matched by a rival thermal reaction, the thermoreversion. This progresses, however, in the case of benzospiropyran, at room temperature by a factor of 10 slower than the light-induced reaction. 

An intermolecular carbenoid reaction followed by intramolecular displacement of acetate gives the clavulanic acid derivative (112) in one step from 4-acetoxyazetidin-2-one (91) (80CC1257). Carbene-induced reactions of penicillins and cephalosporins have been reviewed (75S547, 78T1731). 

Instead of using thermal energy to trigger the hydrogen abstraction mechanism, photo-induced reactions can be also be used to successfully crosslink acrylic PSAs [74-76], In this case, photoactive compounds, such as for example those containing benzophenone, anthraquinone or triazine nuclei are compounded with the polymer or copolymerized as one of the monomers. After drying, the adhesive... 

The Barton-Zard reaction refers to the base-induced reaction of nitroalkenes 1 with alkyl a-isocyanoacetates 2 to afford pyrroles 3. Solvents used are THF or alcohols (or mixtures) and the reaction often proceeds at room temperature. 

The thermally induced reactions of endiandric acids F and G methyl esters (59 and 60) were followed in a similar fashion... 

An excess of a standard solution of iron(II) must therefore be added and the excess back-titrated with standard cerium(IV) sulphate solution. Erratic results are obtained, depending upon the exact experimental conditions, because of induced reactions leading to oxidation by air of iron(II) ion or to decomposition of the persulphate these induced reactions are inhibited by bromide ion in concentrations not exceeding 1M and, under these conditions, the determination may be carried out in the presence of organic matter. 

The light-induced reaction of pentacarbonyliron with oxepin or 2,7-dimethyloxepin results in the formation of small quantities (3-5 %) of a tricarbonyliron complex of the seven-mem-bered heterocycle.253,251 The main products are benzene (o-xylene) and phenol (2,6-dimethyl-phenol). When 1-benzoxepin is treated with pentacarbonyliron, the tricarbonyliron complex is obtained in 22% yield.254... 

Occasionally, these thermally induced reactions give rise to complex mixtures of products and hence are not of any great preparative value. For example, 1-mcthylindolc with dimethyl acetylenedicarboxylate in acetonitrile yields seven products including the 1-benzazepine 8 (14%), the 1-methyl derivatives of the cis- and /rwK-indolylacrylates 3. a [4 + 2] cycloadduct of the 1-benzazcpinc with the alkyne dicster (see Section 3.2.2.5.3.), and dimethyl l-mcthyl-2-(l-methylindol-3-yl)-2,3-dihydro-l //-l-benzazepinc-3,4-dicarboxylate (9).21 This last product, which is the major product if the cycloaddition is carried out in acetonitrile containing trace amounts of water,21 has been obtained earlier.143 but was incorrectly formulated. 

Intramolecular cyclization can yield fluorinated phenoxazines by a Smiles rearrangement (86IZV1855) and 2,3-dihydro-l,4-benzodioxins by a base-induced reaction [81JFC(18)483]. 

Ring expansions of vinylaziridines with carbon monoxide are a useful transformation with which to produce lactams. I11 1974, a light-induced reaction between vinylaziridine 256 and Fe(CO)5, forming the 7t-allyltricarbonyliron lactam complex... 

Allylic transposition is observed in fluoride-induced reactions of allyl(trifluoro)silanes50 and allyl(trichloro)- and allyl(trialkoxy)silanes in the presence of hydroxylic promoters, e.g., 1,2-benzenediol51,52. Pentacoordinated silicates are believed to be involved53. 

In contrast, ( )- and (Z)-2-butcnyl(trifluoro)silanes undergo stereoselective fluoride-induced reactions with aldehydes to give anti- and. sy -products, respectively37. 

Efficient asymmetric transfer is also observed for 1,2-benzenediol induced reactions of a-sub-stituted (Z)- and ( ,)-allyl(trialkoxy)silanes prepared by hydrosilation of conjugated dienes, although in this case the electrophile attacks the C-C double bond of the allylsilane syn with... 

The stereoselectivity of the boron trifluoride induced reactions was initially discussed in terms of open-chain, antiperiplanar transition states66. However studies of Lewis acid induced intramolecular allylstannane-aldehyde reactions are supportive of a synclinal process56,67. 

Allenylstannancs also provide sw-products stereoselcctively from their Lewis acid induced reactions with a-branched aldehydes86. 

Good Cram selectivity is observed for Lewis acid induced reactions between allylstannanes and aldehydes with alkyl-substituted a-chiral centers66,87. This enhanced Cram selectivity may be due to the effect of the Lewis acid on the trajectory of nucleophilic attack on the aldehyde66. 

For Lewis acid induced reactions between a-alkoxyaldehydes and allylstannanes, either Cram or chelation control is observed depending on the choice of Lewis acid and the O-substituent88. 

Excellent chelation control was observed using tributyl(2-propenyl)stannane and a-benzyloxy-cyclohexaneacetaldehyde with magnesium bromide or titanium(IV) chloride, whereas useful Cram selectivity was observed for boron trifluoride-diethyl ether complex induced reactions of the corresponding ferr-butyldimethylsilyl ether89. 

The boron trifluoride-diethyl ether complex induced reaction of 2-butenyl(tributyl)-stannane and 3-(/er/-butyldimethylsilyloxy)-2-methylpropanal gave predominantly the nonchelation-controlled yyn-product93, whereas with the analogous 3-benzyloxyaldehyde, 2-propenyl-tin trichloride, generated in situ from tributyl(2-propenyl)stannanc and tin(IV) chloride, gave the chelation-controlled product93. 

Chiral amides of 2-(tributylstannylmethyl)-2-propenoic acid show useful stereoselectivity in their Lewis acid induced reactions with aldehydes, and the products have been converted into optically active a-methylenelactones95. 

Boron trifluoride-diethyl ether complex induced reactions of both (E)- and (Z)-tributyI(3-methoxy-2-propenyl)stannane with aldehydes give. vj-w-products with useful slereoselectivi-... 

Useful Cram selectivity is observed for Lewis acid induced reactions between 3-alkoxyallylstan-nanes and aldehydes with alkyl substituted a-stereogenic centers116. 

The titanium(IV) chloride induced reaction of an a-methyl-y-carbamoyloxyallylstannane, which is believed to involve the in situ generation of a chiral a-carbamoyloxytitanium species, gave products 3 and 4 in yields of ca. 85 %, whose configuration was determined by the reagent, not by the aldehyde118. 

The Lewis acid induced reaction of silyl enol ethers and silyl ketene (thio)acetals with 4-acetoxyazetidinones is often used for introduction of a carbon substituent in the 4-position of the jS-lactam ring. Numerous examples are known, both with and without substituents at nitrogen, some of which are shown. 

Apparently the Lewis acid induced and the fluoride-induced reactions of allylsilanes with enones follow different pathways. The perpendicular approach of the nucleophilic allylsilane... 

Alicyclic ew-dialkyldiazenes are very thermolabile when compared to the corresponding tram-isomers, often having only transient existence under typical reaction conditions. It has been proposed49 that the main light-induced reaction of the dialkyldiazenes is tram-cis isomerization. Dissociation to radicals and nitrogen is then a thermal reaction of the cis-isomer (Scheme 3.19),... 

Various light-induced reactions including hydrogen atom abstraction, electron transfer and (3-scission occur under the influence of UV light. Certain... 

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