Allylic chlorides, synthesis

Ketones can be prepared by trapping (transmetallation) the acyl palladium intermediate 402 with organometallic reagents. The allylic chloride 400 is car-bonylated to give the mixed diallylic ketone 403 in the presence of allyltri-butylstannane (401) in moderate yields[256]. Alkenyl- and arylstannanes are also used for ketone synthesis from allylic chlorides[257,258]. Total syntheses of dendrolasin (404)f258] and manoalide[259] have been carried out employing this reaction. Similarly, formation of the ketone 406 takes place with the alkylzinc reagent 405[260],... 

Organoboranes are reactive compounds for cross-coupling[277]. The synthesis of humulene (83) by the intramolecular cross-coupling of allylic bromide with alkenylborane is an example[278]. The reaction of vinyiborane with vinyl-oxirane (425) affords the homoallylic alcohol 426 by 1,2-addition as main products and the allylic alcohol 427 by 1,4-addition as a minor product[279]. Two phenyl groups in sodium tetraphenylborate (428) are used for the coupling with allylic acetate[280] or allyl chloride[33,28l]. 

Coupling of allyl chloride with the (2 -alkenylpentafluorosilicate 463 using Pd(OAc)j as a catalyst at room temperature gives a 1,4-diene in good yields. The reaction has been applied to the synthesis of recifeiolide[299]. 

Compound 1, 2,2-diniethyl-4-pentenal, has been prepared by the Claisen rearrangement route described above and by reaction of isobutyraldehyde with allyl chloride in the presence of aqueous sodium hydroxide and a phase-transfer catalyst. Both routes are applicable to the synthesis of a variety of substituted 4-pentenals. 

Allyl chloride is quite reactive toward nucleophilic substitutions, especially those that proceed by the Sn2 mechanism, and is used as a starting material in the synthesis of a variety of drugs and agricultural and industrial chemicals. 

After succeeding in the direct synthesis of allyidichlorosilane hy reacting elemental silicon with a mixture of allyl chloride and hydrogen chloride in 1993," Jung el cil. reinvestigated the Friedel-Crafts reactions of benzene derivatives with allyidichlorosilanes in detail (Eq. (2)). 

Allylic chlorides can also be used as coupling partners, as shown by Lu and Liu [137]. In addition, the domino process could be used for the synthesis of benzylidene pyrrolidines, as shown for the reaction of 6/1-285 with benzylidene malonate... 

Recent trend in the synthesis of olefinic pheromones is the use of transition metal-catalyzed cross coupling reaction for carbon-carbon bond formation. Scheme 8 summarizes a synthesis of the termite trail marker pheromone, (3Z,6Z)-3,6-dodecadien- l-ol (2) by Oehlschlager [19]. The key-step is the palladium-catalyzed cross-coupling of allylic chloride A and alkenylalane B. 

Our approach to the synthesis of model compounds, suited for the generation of carbenes, which are bound to the bridgehead of a strained bicyclic system, used the facile synthesis of [n.l.ljpropellanes, which we developed some years ago. Starting from substituted allyl chlorides 35, dibromocarbene addi-... 

Prior to his work with internal alkynes, Larock found that o-thallated acetanilide undergoes Pd-catalyzed reactions with vinyl bromide and allyl chloride to give (V-acetylindole and N-acetyl-2-methylindole each in 45% yield [409]. In an extension to reactions of internal alkynes with imines of o-iodoaniline, Larock reported a concise synthesis of isoindolo[2,l-a]indoles 313 and 314 [410]. The regioselectivity was excellent with unsymmetrical alkynes. 

The complexes of the composition [ Ir( t-X)(diene) 2], where X = halogen, OH, OMe (e.g. [IrCl(CO)(cod)]) appeared to be very effective catalysts for the hydrosilylation of allyl chloride by trialkoxy- and alkylalkoxy-silanes [22]. Other iridium complexes have been subsequently reported as catalysts for the synthesis of silane... 

If further acidic C—H bonds in the molecule cause problems, the tin-trick can be applied. The asymmetric deprotonation of a bifunctional carbamate (39a) is accomplished at an early stage and the masked carbanionic centre carried through the synthesis as a stan-nyl group. For instance, the (S)-5-silyloxy-l-tributylstannyl-pentyl carbamate 39b (> 95% ee) was produced by the usual means and converted by standard steps via the aldehyde 78 into the allyl chloride 79 (equation 17) . Lithiodestannylation of 79 by n-BuLi proceeds faster than reductive lithiation in the allylic position to form the lithiocarbamate 80,... 

A similar approach was taken for the synthesis of 45 by Miyaura. " Shaughnessy and Booth synthesized the water-soluble alkylphosphine 46, and found it to provide very active palladium catalysts for the reaction of aryl bromides or chlorides with boronic acids. The more sterically demanding ligand 47 was shown to promote the reactions of aryl chlorides with better results than 46. Najera and co-workers recently reported on the synthesis of di(2-pyridyl)-methylamine-palladium dichloride complexes 48a and 48b, and their use in the coupling of a variety of electrophiles (aryl bromides or chlorides, allyl chlorides, acetates or carbonates) with alkyl- or arylboronic acids very low catalyst loadings at Palladium-oxime catalysts 8a and 8b) have also been developed. In conjunction with... 

The same strategy has been used by Williams (90JA808) in his synthesis of brevianamide B. The aldehyde (82), prepared enantioselectively from L-proline, was converted to the silyl ether. Acylation of this (BuLi, ClC02Me) gave the carbomethoxy derivative as a mixture of diastereo-mers, which was alkylated by gramine. As before, an enolate alkylation (Sn2 ) on an allyl chloride derived from the above gave the tricyclic compound, which could be transformed to brevianamide B (Scheme 24). 

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