Allyl and Vinyl Halides

The bridgehead chlorines in 1,2,3,4-tetrachloronorbornene (90) are not removed, although they are allylic in the hydrogenation over Raney Ni in methanol in the presence of potassium hydroxide, only the vinylic chlorines are lost to give 1,4-dichloronorbornane (eq. 13.124).224 

Similarly, 1,2,3,4,7,7-hexachloronorbornene (91, X = Cl) and l,2,3,4-tetrachloro-7,7-dimethoxynorbornene (91, X = OMe) are hydrogenated without losing the allylic chlorines in the hydrogenation over Pd-C in ethanol in the presence of triethylamine only the vinylic chlorines are removed (eq. 13.125).225 The 7,7 bridge chlorines of the product may be further reduced to 1,4-dichloronorbornane by diphenyltin dihydride in diglyme at 110-120°C. 

Hydrogenation of the trifluorostyrene 92 over platinum oxide results in partial defluorination during saturation of the side chain (eq. 13.126).226 

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Cooper(I) carboxylates give esters with primary (including neopentyl without rearrangement), secondary, and tertiary alkyl, allylic, and vinylic halides. A simple Sn mechanism is obviously precluded in this case. Vinylic halides can be converted to vinylic acetates by treatment with sodium acetate if palladium(II) chloride is present. ... 

For symmetrical coupling of allylic and vinylic halides or alcohols, see also page 77, Section 1. 

The palladium-catalyzed ring heteroannulation of allenes 278 by tosyl amide and amine-containing allyl and vinyl halides (e.g., 277) provided a facile route to a variety of azepanes (e.g., 279) (Equation 39) <2003JOC6859> in the case of iV-tosyl-(2-iodophenyl)ethylamine, benzazepines are formed. 

Benzyl, allyl and vinyl halides were electrochemically transformed to their corresponding silanes (52-55) in the presence of trialkylsilyl chlorides as seen in equation 36. 

The Stille reaction of fluorovinyltin reagents offers the greatest synthetic flexibility, and reactions with alkanoyl (e.g., formation of 5 ), aryl (e.g., formation of 6 ), allyl and vinyl halides have been reported. Stereospecific destannylation reactions ofa-fluorovinyltin reagents include protonolysis, deuterolysis and iodination reactions. Electrophilic fluorination of the C —Sn bond has also been reported. 

Berkessel, A., Menche, D., Sklorz, C. A., Schroder, M., Paterson, I. A highly enantioselective catalyst for the asymmetric Nozaki-Hiyama-Kishi reaction of allylic and vinylic halides. Arrgew. Chem., Int, Ed, Engl, 2003,42,1032-1035. 

The use of ultrasound allows the direct in situ formation of benzyllithium from benzyl bromide while normally Wurtz coupling predominates with this halide. (See e.g. p. 79 [15]). Condensation, e.g. with acetophenone gives the expected product in 95% yield. Also allylic and vinylic halides undergo clean... 

RELATIVE REACTIVITIES OF ALKYL, ARYL, ALLYL AND VINYL HALIDES TOWARDS SUBSTITUTION REACTIONS. 

Berkessel et al. have demonstrated that salen ligand 12 based on e Jo,e c/o-2,5-diaminonorbornane (DIANANE) promoted efficient and highly enantioselective catalytic NHK reactions of various allylic and vinylic halides to aromatic and aliphatic aldehydes with up to 92% ee. ... 

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