Halides cinnamyl

Interaction of Ni11 ions with amino acids is also important for asymmetric synthesis of amino acids. A convenient large-scale asymmetric synthesis of enantiometrically pure trans-cinnamyl-glycine and -o-alanine via reaction of cinnamyl halides with Ni11 complexes of a chiral Schiff base of glycine and alanine has been elaborated.1711 Similar procedures have been applied to other amino acids as well.1712... 

Potential difference in reactivity between two G-B bonds allowed the transformation of l,2-bis(boryl)-l-alkenes to 1-alkenylboranes via a cross-coupling with the aryl, 1-alkenyl, benzyl, and cinnamyl halides (Equation (23)).211-213 This tandem procedure synthetically equivalent to a yy/z-carboboration of alkynes was used for synthesizing Tamoxifen derivatives via stepwise double coupling with two of the G-B bonds.212,213 Hydrogenation of the resulting bisborylalk-enes with a chiral rhodium catalyst is synthetically equivalent to an asymmetric diboration of alkenes (Equation (24)).214... 

Although the reaction was often accompanied with a double-coupling product at both C-B bonds (5-10%), high terminal-selectivity of over 99% was readily achieved in the coupling reaction with aryl, 1 -alkenyl, benzyl, and cinnamyl halides. The utility of the stepwise, double-coupling procedure was demonstrated in the parallel synthesis of Tamoxifen derivatives on solid support... 

Asymmetric allylation of cinnamyl halides, alkylation of alkynyl epoxides, and 1,4-addition of nitro olefins" are also successfully demonstrated by combination of an organozinc reagent and a chiral copper phosphoramidite. 

Allylic halogenides containing an additional internal functional group in a suitable position, e. g., an alkene moiety or a hydroxy group, produce the corresponding cyclopentenone derivatives or lactones, respectively, via palladium-catalyzed carbonylation [43]. Related cyclocarbonylations of cinnamyl halides or acetates to form polycyclic aromatics such as naphthol derivatives have been reported (eq. (15)). Moreover, the synthetic utility of the method was demonstrated by the synthesis of acetoxybenzofurans, acetoxyindoles, and acetoxycarbazoles [44]. 

Bu"3SnLi-Et2AlCI, In none of these cases, however, has diastereoselectivity exceeded 75 25, It is probable that these reagents are configurationally unstable, as implied by the results summarized in Scheme 2j.32b.77 j jj noteworthy that cinnamyl halides display very high anti selectivity with SnClj-AI and Sn-Af in contrast to the poor results obtained with the crotyl systems. ... 

This reaction profile, also called carbonylation, governs the reactivity of Pd-carbonyl complexes. Anionic M[Pd(CO)l3], for instance, catalyzes the reductive carbonylation of esters.f On the other hand, Pd(CO)(PPh3)3 was reported to catalyze the carboxymethy-lation of organic halides and the cyclocarbonylation of cinnamyl halides.f " However, the Pd-CO complexes are most often generated in situ from preformed alkyl -palladium complexes and CO under stoichiometric or catalytic conditions, for example, in the copolymerization of alkenes and CO. Decarbonylation reactions also involve the intermediacy of Pd-CO complexes. In this case, migratory deinsertion (Sect, n.3.1), that is, the microscopic reversal of the migratory insertion, takes place. 

The effect of the leaving group was briefly examined, but cinnamyl bromide gave a substantially lower ee (38%). Cinnamyl dimethyl phosphonate, or acetate, gave very poor results. The cyclohexyl-substituted allylic acetate 21, on the other hand, afforded a completely y-selective reaction, but the product turned out to be racemic. Changing the Grignard reagent halide from bromide to either chloride or iodide resulted in very low ees. 

When using the corresponding cinnamyl compound, regioselectivity depends on the size of the alkyl halide. The a-product predominates with iodomethane (90% yield, d.r. >96 4, S) or iodoethane (79% yield, d.r. >96 4, 5), whereas 2-iodopropane attacks the y-position preferably (85% yield, d.r. 89 11, R)5- 52 53. Introduction of other chiral auxiliaries gave no improvement53. 

J. F. Normant, J. F. Enantioselective carbome- 484 talation of cinnamyl derivatives new access to chiral disubstituted cyclopropanes. Configurational stability of benzylic organozinc halides. Chem. Eur. J. 1999, 5, 2055-2068. 485... 

Compounds of type LXXIII cannot be made by the rearrangement of the 7-substituted allyl ethers, because these compounds yield LXXIV by inversion. a,7-Dimethylallyl bromide,16 7,7-dimethylallyl bromide,29 cinnamyl chloride,84 and phytyl bromide 86 (a vitamin K synthesis) have been used in C-alkylation procedures. The silver salt of 2-hydroxy-l,4-naphthoquinone is converted to a mixture of C-alkylation product and two isomeric ethers by treatment with allylic halides and benzyl halides. ... 

Probably, also in the anion 31 and in the alkylation transition state 12b one methyl group is turned inside and shields the bottom side of the molecule effectively. Since these alkyl halides give the highest inductions that contain an extended rc-system (benzyl, cinnamyl, phenylpropargyl, etc.) it is plausible to assume also for the incoming alkyl group the folded conformation (cf. 12b). 

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