Halogeno-alkenes

Halogeno-alkenes.- The photochemical behaviour of AJdrm (30a) is complex. A reinvestigation of the irradiation of this cyclodiene insecticide in hexane has isolated two new photo products (30b) and (31). Irradiation in acetone also provides surprises and the two new adducts (32) and (33) have been identified. The influence of triethylamine on photodehalogenation of cyclodiene insecticides has also been evaluated. Irradiation appears to bring about selective dehalogenation at C-11 in (30a) yielding a 9 1 mixture of the products (34a) and (34b). This stereoselective loss of chlorine is also seen with Dieldrin (35) and Endrin (36).  

Photoreduction products are obtained on the irradiation of the bromocamphene derivative (37) in non polar media. A vinyl radical is thought to be involved. In polar media, however, ether derivatives are produced via a carbocation intermediate and trapping by alcohol.  

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More evidence has appeared showing that the olefin metathesis reaction can tolerate the presence of functional groups. The catalytic system Re207-Al203, promoted by a small amount of tetramethyltin, effects metathesis of olefins in fair yield (17—40%) in the presence of unsaturated ethers and ketones, alkenyl esters, and halogeno-alkenes. The reaction is performed in carbon tetrachloride as solvent at room temperature over 6 h. Electro-reduction of tungsten hexa-chloride with an aluminium anode in halogenated solvents appears to form a complex suitable for a clean metathesis, exemplified by the conversion of pent-2-ene into its equilibrium mixture with but-2-ene and hex-3-ene. ... 

Reactions with Simple Alkenes and Aromatic Compounds.—A wide range of conditions continues to be used to form phosphorus-carbon bonds between halogeno-phosphines and alkenes or benzene derivatives. A selection of such reactions (Scheme 2) is outlined for the preparation of the compounds (17)—(23).22-26... 

Borazines, particularly polymeric compounds, have been extensively investigated as preceramic materials from which coatings and fibers of boron nitride can be produced upon thermolysis. B-aryl and halogeno-amino borazines are reported to have use as fire retardants in cotton and nylon textiles. Other reported uses for borazines are as epoxy resin catalysts, polymerization inhibitors of unsaturated alcohols and esters, and catalysts for polymerization of alkenes (95). 

Other synthetic routes reported involve the interactions of trifluoro-phosphine metallates and iodine (method E), displacement of carbon monoxide, alkenes, etc. by PF3 from the corresponding halide complexes (method F), addition of PF3 to dinuclear halogeno-bridged PF3 complexes at low temperatures (method G), and treatment of a metal hydrido- PF3 complex with iodoform (method H). 

Other synthetic routes to alkene-metal complexes reported in the literature involve bridge cleavage reactions of halogeno complexes (method F), facile intermolecular scrambling reactions involving metal-alkene and metal-PF3 complexes (18, 81) (method G) (Scheme 4), and the coupling together of two alkyne units to afford a metallo-cyclopentadiene derivative (method H). 

Hi. Carbon-silicon bonds. Following the earlier reports mentioning the palladium-catalysed addition of organosilylstannanes to alkynes or isonitriles , Mori and coworkers realized tandem transmetallation-cyclization reactions with bifunctional halogeno triflates and Bu3SnSiMe3 18. The reactivity of 18 under palladium catalysis was used for the silylstannylation of alkenes or the synthesis of allylic silanes via a three-component (aryl iodide - - diene - - 18) coupling reaction. Recently, a similar... 

As expected, halogeno compounds also undergo [l,2,3]-eliminations (cf. footnote 68)). Thus, in the gas phase the dehydrochlorination of neopentyl chloride (59) inter alia yields the alkene 13142). From gem-dihalogen alkylcyclopropanes such as 132,... 

The Perkow reaction has been used to generate a wide range of vinyl phosphates. Reaction of trialkyl phosphites with a-halogeno-ketones provide vinyl phosphates.1-5 Alkenes are produced via reduction of the dialkyl enol phosphate using either sodium or lithium in liquid ammonia. 

Further papers have appeared on the coupling of halogeno-pyrimidines, in particular iodopyrimidines, and terminal alkenes and alkynes. For example, palladium (II) acetate with a... 

Oxazines. - =-Nitrosostyrenes(320 R = Ar) form cycloadducts with alkenes to give 3-aryl-5,6-dihydro-4H-1,2-oxazines (321 R1 = Ar) vinylnitroso compounds similarly form 1,2-oxazines by addition to alkenes. These cycloaddition reactions are in general both regio-and stereo-selective. The nitroso compounds are generated in situ by treatment of the corresponding halogeno-oximes (319) with base.26 ... 

Essentially, the Michaelis-Arbuzov reaction proceeds well with primary alkyl halides and at least moderately well with secondary halides, the reactivity of the halogen being in the order I > Br > Cl, alkyl fluorides normally being unreactive (the reactive polyfluo-roalkanes and alkenes do undergo reactions with trialkyl phosphites and afford halogeno-... 

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