Stereo-selective synthesi

The addition of organolithium compounds27 to allylic alcohols in the presence of TMEDA is a prep-aratively useful method which allows a high regio- and stereo-selective synthesis of alcohols. Several side reactions can be observed depending on the structure of the allylic alcohol (14 Scheme 7). If the... 

Regio- and stereo-selective synthesis of annulated arene heterocycles and carbocy-cles having a halo functionality is accomplished by Sm(OTf)3-catalysed alkylation of (S) arenes by a tethered alkene group using /V-halosuccinimide as a halogen source [e.g. 

Scheme 4. Regio- and stereo-selective synthesis of coumarinolignans using Ph2SeO...

Reduction of double and triple bonds. The final step in a highly stereo.selective synthesis of 4-methylhex-3-m-ene-l-ol(2) involved reduction of the dienol (1). This... 

Selective reduction of allyl sulfides implies that no scrambling of the carbon-carbon double bond occurs during the process. Effectively this has proved to be the case especially when lithium in ethylamine is used, and the method has allowed the regio- and stereo-selective synthesis of a large variety of 1,5-dienes including squalene (Scheme 25, entry a), mukapolide (Scheme 25, entry b), dendrolasin (Scheme 25, entry c), the basic nucleus of crassin acetate (Scheme 25, entry d) from 7,7-dialkylallyl sulfides and allyl halides, and also of 1,5-enynes " from propargyl sulfides and allyl halides (Scheme 34, entry b). 

The use of enals in nickel-promoted intermolecular couplings was initially limited to stoichiometric [3 -1- 2]/[2 + 1] cycloadditions [26], This limitation was overcome with the development of a Ni(COD)2/PCy3/R3SiH/THF reaction system, whereby the reductive coupling of alkynes and enals was achieved to afford a highly chemo- and stereo-selective synthesis of Z-enol silanes (Scheme 8.6) [27]. 

Additions of organometallic reagents to 1-alkynes continue to play a prominent role in the regio- and stereo-selective synthesis of olefins. A convenient procedure for the stereospecific synthesis of trisubstituted olefins, based on Normant s work on the addition of alkyl copper(l) complexes to 1-alkynes, is outlined in Scheme 10. The use of House s dimethyl sulphide-copper(i) bromide complex minimizes... 

A. Dandia, A. K. Jain, A. K. Laxkar, D. S. Bhati, Tetrahedron Lett. 2013,54,3180-3184. A highly efficient protocol for the regio- and stereo-selective synthesis of spiro pyrrohdine and pyrrolizidine derivatives by multicomponent reaction. 

A review has been published on the regio- and stereo-selective synthesis of C-glycosides from glycal-Pd complexes, and the reaction between reducing sugars and carbonyl compounds which results in C-glycosides has been referred to in a further review. ... 

The scope of regio- and stereo-selective synthesis of vinylallenes by 1,5-(>S )-substitution of enyne acetates and oxiranes with organocuprates has been explored the products are usually obtained as mixtures of E- and Z-isomers (Scheme 12), ° Optimum conditions for stereoselective alkynylation of trans-2,3-epoxy sulfides at C(2), with double inversion of configuration, on reaction with alkynylaluminiums (Scheme 13) have been sought. 

Nagasawa. K., Shimizu, 1., and Nakata, T. (1996) Total synthesis of preswinholide A. 1. Stereo-selective synthesis of the C11-C23 segment. Tetrahedron Lett., 37, 6881-6884. 

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