Alkenyl cuprate

The reaction of propargylic chiral acetals with a catalytic copper reagent (RMgX/5% CuX) provides the expected alkoxy allenes in quantitative yield (Table 3)61. The diastereomeric excess is highly dependent on the size of the ring of the acetal and on the type of substituents it contains. The best diastereomeric excess is 85% with the acetal derived from cyclooctanediol. The use of lithium dimethylcuprate results in 1,2-addition lo the triple bond and the resulting lithium alkenyl cuprate bearing a cyclic acetal does not eliminate even at reflux temperature ( + 35°C). 

Stereodehned alkenyl cuprates add to alkynes in syn fashion to result in 1,3-dienes of predictable stereochemistry288. Naso and coworkers used this method for the synthesis... 

It appears that neither the lithium carbenoid pathway nor the cyclopropanation of buta-trienes are general routes to [3]radialenes. More successful is the cyclotrimerization of 1,1-dihaloalkenes via copper or nickel carbenoids, provided the substituents at the other end of the C=C double bond are not too small. Thus, tris(fluoren-9-ylidene)cyclopropane 27 was formed besides butatriene 28 from the (l-bromo-l-alkenyl)cuprate 26 generated in situ from (9-dibromomethylene)fluorene (Scheme 3)10. The cuprate complexes formed... 

Radialenes represent the biggest and best known subset of the radialene family this is not surprising in view of the fact that more methods to prepare them exist than for any other class of radialenes. The major strategies are the transformation of appropriate cyclobutane derivatives, the thermal or Ni(0)-catalyzed cyclodimerization of butatrienes or higher cumulenes and the cyclotetramerization of (l-bromo-l-alkenyl)cuprates. 

A(-(Arylthiomethyl)amines, which are easily prepared and reportedly have better shelf stability than the corresponding )V-(alkoxymethyl)amines, have also been utilized to prepare tertiary amines. Alkenyl cuprate addition to )V,A -diethylphenylthiomethylamine produces allylic amines in high yield (entry 1, Table 6). Both alkenyl groups of the cuprate react. 5-(Dialkylaminomethyl) dithiocarbamates (entry 2, Table 6), sulfonates (entry 3, Table 6) and amides also generate iminium salts in situ. Of a variety of amides examined, imides such as dialkylaminomethyl-succinimides (entry 4, Table 6) and -phthali-mides provide the best overall yields. Organolithium reagents are rarely utilized in aminomethylation reactions. However, )V-chloromethylamines condense readily with lithiated anisole derivatives (entry S, Table 6). ... 

Mercury, Zinc, and Copper. The thermal decomposition of 2-thienylmercury thiocyanate, azide, acetate, and trifluoromethylsulphonate has been investigated. Thienylmercury derivatives have been cross-coupled with primary and secondary alkyl- and alkenyl-cuprate reagents. 2-Thienylzinc chloride has been coupled with iodobenzene and vinyl bromide, using Pd catalysis. ... 

In analoger Weise lassen sich auch Bis-[l-alkenyl]-cuprate carboxylieren376. 

Cu(I)-mediated 1,2-metalate rearrangement to alkenyl cuprate 69 from which alkenyl iodide 70 was isolated upon treatment with iodine before final cycHzation to manoahde 71 (Scheme 19) (2003JOC4008). 

Aryl-, alkenyl-, and alkyl-mercurials react by cross-coupling with primary and secondary alkyl- and alkenyl-cuprate reagents to provide the first truly general... 

Metal-catalysed ring-opening reactions of lactones can be useful in synthesis. For example, a one-pot procedure for the formation of (Z)-4-alkenoic acids, the esters of which are components of various perfumes and flavours, relies on the cis nature of addition of dialkylcuprates to acetylenes to afford (Z)-alkenyl-cuprates. These cuprates induce ring opening of -propiolactone in a regioselec-tive manner by alkyl oxygen fission to give the desired compounds in excellent yield. ... 

A. Alexakis, G. Cahiez, and J. F. Normant, Tetrahedron, 1980, 36, 1961. (Z)-Alkenyl cuprate reactions with various electrophiles, e.g., CO2, epoxides, aldehydes, ot,jS-enones, and alkynes. 

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