Remote stereocontrol

Due to the distance between the stereogenic center and the place of the nucleophilic attack, the enantioselective 1,5-substitution of chiral enyne acetates constitutes one of the rare cases of remote stereocontrol in organocopper chemistry. Moreover, the method is not limited to substrate 51, but can also be applied to the synthesis of enantiomerically enriched or pure vinylallenes 53-57 with variable substituent patterns (Scheme 2.20) [28]. 

Scheme 4.13 Asymmetric synthesis of vinylallenes by the remote stereocontrol.

Stereochemical Results External Asymmetric Induction/Remote Stereocontrol 193... 

While the process works for a great number of conjugated dienes, a few, such as 1,3-cyclopentadiene and those acyclic dienes that have an oxygen substituenl in an allylic position, did not give a chloroacetoxylation product.23 Control of the 1,4-relative stereochemistry and preparation of compounds analogous to the title compounds also work for acyclic dienes,23 5 This process was used to obtain remote stereocontrol in acyclic systems and applied to the synthesis of a pheromone.5... 

Barbero, A. Pulido, F. J. Rincon, J. A. Cua-drado, P. Galisteo, D. Martinez-Garcia, H. Remote stereocontrol in carbonyl additions promoted by vinylstannanes. Angew. Chem. 

Furthermore, high remote stereocontrol is observed by treating the protected 2- or 3-methylpenlenols with tin(IV) chloride. The resulting tetrahydrofuran system is predominantly 1,2- or l,3-.s v i-configurated due to the equatorial position of the methyl substituent in the cationic intermediate34. 

Tricyclizations including seven-membered ring closure are rarely described. Initiation of the reaction by a tetramethylallylic cation leads to a six-six-seven-membered ring system via a b-endo-b-endo-l-endo cyclization according to Markovnikov s rule. Two diastereomers are formed due to the lack of remote stereocontrol by the initiating cation66. 

Dianionic Claisen rearrangements of (E)- and (Z)-butenyl jS-hydroxy esters afford acyclic systems I and 2 containing three stereogenic centers. The reactions proceed with remote stereocontrol (see Section 1.6.3.1.1,5.1.1. p 3481)50S-509. 

More remote stereocontrol is achieved in the hydroboration of 1,4-. 1,5- and 1.6-dienes with thexylborane [(l.O-trimethylpropyljborane]32 6 ... 

Clayden J, Lund A, Vallverdu L, Helliwell M (2004) Ultra-remote stereocontrol by conformational communication of information along a carbon chain. Nature 431 966-971... 

Byrne L, Sola J, Boddaert T, Marcelli T, Adams RW, Morris GA, Clayden J (2014) Foldamer-mediated remote stereocontrol >1,60 asymmetric induction. Angew Chem Int Ed 53 151-155... 

It has been observed that in basic media aromatic hydrocarbons and benzylmethyl ethers bound to -Cr(CO)3 are easily nitrosated at the benzylic position. A review type article discusses the stereoselective manipulation of acetals derived from o-substituted benzaldehyde chromium tricarbonyls. The diastereoselective synthesis of a range of substituted cyclohexadienes has been reported from enandomerically pure (2-phenyl-4,S-dibydroxazole)chromium tiicaibonyl complexes. Aromatic nucleophilic substitution on halaogenoarene tricarbonylchromium complexes gives rise to a series of complexed aniline derivatives. The diastereoselective 1,4-addition of organocuprates to o-substituted-phenyI-(E)-enone chromium carbonyl conq)lexes provides a new method for remote stereocontrol at the 1,3, and S-positimis of the side chains. ... 

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