Diastereoselectivity in the addition of allylzinc reagents to delta-alkoxy-gamma,delta-disubstituted alkenyllithium compounds.

The carbometalation reaction of allyl- and crotylzinc bromide with metalated disubstituted homoallylic ethers gives tri- or tetrasubstituted 5-hexenyl ethers with excellent control of the diastereoselectivity. The stereochemistry of this reaction is discussed and has been attributed to an early transition state with chelation to the oxygen atom in the energetically favored conformer as the stereodetermining step.

Diastereoselective and Enantioselective Intramolecular Amino-Zinc-Enolate Carbometalation Reactions. A New Polysubstituted Pyrrolidines Synthesis.

The amino-zinc-enolate cyclization allowed a new and straightforward route to polysubstituted pyrrolidines from simple starting materials. From this study, we have been able to determine, for the first time, the stereochemical influence of the substituents on the ring in the carbocyclization reaction. The diastereoselectivity thus obtained was explained by a chairlike amino-zinc-enolate transition state.

Amino Zinc Enolate Carbocyclization Reactions. New Access to Polysubstituted Piperidine Derivatives.

Various N-pent-4-enylglycine methyl esters have been submitted to carbocyclization of their zinc enolates onto the unactivated double bond. The cyclization to substituted pipecolic esters is highly stereoselective. In most cases, substitution of the pent-4-enyl moiety on various sites leads to a single isomer, hence a way to di-, tri-, tetra-, or pentasubstituted piperidines.

1,1-Dimetallic reagents for the elaboration of stereoselectively di- or trisubstituted linear substrates.

Although gem-dimetallic species have been known for a long time, and reacted once or twice with electrophiles, the allyl zincation of substituted vinyl metals has emerged as a particularly efficient access to such species. This is due to a high face selectivity, in the addition to the C=C bond, which can be governed by vicinal or more remote heteroatoms. This strategy has some aspects in common with the well-known allylations or aldol condensations to carbonyl derivatives.

Comparative study of the diastereoselective addition of allenyl zinc reagents to alpha-alkoxy (or silyloxy) aldehydes and imines. A straightforward synthesis of amino alcohols from imines.

The addition of allenylzinc bromides to alpha-chiral imines proceeds with very high diastereoselectivity. This result is in contrast with the addition to the corresponding aldehydes, leading to poor diastereoselectivity. The anti/anti adducts are explained by Felkin-Ahn and Gaudemar-Yamamoto models of the transition state.

Fritsch-Buttenberg-Wiechell rearrangement in the aliphatic series.

[reaction: see text] Substituted vinylidene zinc carbenoids undergo a Fritsch-Buttenberg-Wiechell rearrangement. The migratory aptitude of the two groups R/R1 was studied by 13C labeling experiments and depends on the degree of substitution in R and R1 groups and on the presence of an oxygen atom in the allylic position.

Synthesis of (Z,Z)-3, 13-octadecadien-1-yl acetate Component of the sex pheromone ofSynanthedon tenuis.

The main component of the sex pheromone of the smaller clear wing moth,Synanthedon tenuis, was synthesized. This iterative synthesis uses the carbocupration of acetylene, followed by the alkylation of the (Z)-alkenyl cuprate or by its reaction with ethylene oxide. (Z,Z)-3,13-octadecadien-1-yl acetate, thus obtained, is of 99.

Synthesis of (Z)-13-hexadecen-11-yn-1-yl acetate Major component of sex pheromone of the processionary moth.

The synthesis of the major component of the sex pheromone of the processionary mothThaumetopoea pityocampa is described. The synthesis uses the carbocupration of acetylene, followed by the coupling with the appropriate 1-iodoalkyne. This synthetic pheromone was shown to be of 98.