Olefin stereospecific

Singlet carbenes add to olefins stereospecifically triplet carbenes add non-stereospecifically. 

Nucleophilic reagents will also effect deoxygenation. Di- or trisubstituted oxiranes have been transformed to olefins stereospecifically with inversion via a phosphobetaine (Eq. 102). ... 

The singlet excited state photochemistry of cyclopropenes is dominated by ring cleavage reactions (Section IV.B.2), but in the triplet manifold [2 -I- 2] cycloaddition is the major pathway. Because of inefficient intersystem crossing the first excited triplet state of a cyclopropene is best populated by sensitization. Despite the added energy involved with these species there is no effective pathway available for ring cleavage in the absence of added olefin stereospecific dimerization to a cis-transoid-cis-tricyclohexane, e.g. 145, occurs. The smallest of the C(3) substituents is endo in the product ". A stepwise... 

The organozinc intermediate is electrophilic but sterically rather hindered. The reaction is characterized by broad generality, olefin stereospecificity, regioselec-tivity, and chemoselectivity [34]. In the presence of a catalytic amount of a non-... 

Treatment of epoxides with lithium diphenylphosphide followed by oxidation gives i3-hydroxydiphenylphosphine oxides which can be fragmented to olefins stereospecifically, thus constituting an olefin inversion (Scheme 2). 

Vinyl halides react with alkyllithiums with the aid of a palladium(O) complex to give olefins stereospecifically in good yields. When Grignard reagents are employed instead of alkyllithium compounds, these reactions can be carried out catalytically with the palladium complex (Yamamura et al., 1975). or/Ao-Alkylated thiobenzophenones can be similarly prepared from 5-donor ligand or/Ao-metalated complexes (H. Alper and J. Kamenof, unpublished results). 

The reaction of alkenyldi-isobutylalane with titanocene dichloride gives dimetalloalkanes (25), which convert ketones into olefins (26) in good yield (around 65%) but with only poor stereoselectivity the general use of heavy main-group elements in the synthesis of terminal olefins and of (Z)- and ( )-olefins stereospecifically has been reviewed by Kauffmann. ... 

Pivaloyl nitrene, generated photolytically from pivaloyl azide, adds to olefins stereospecifically in its singlet state and stereoselectivily in its triplet state. Dichloro-... 

Corey, E. J. Katzenellenbogen, J. A. Posner, G. H. New Stereospecific Synthesis of Trisubstituted Olefins. Stereospecific Synthesis of Farnesol J. Am. Chem. Soc. 1967, 89, 42454247. Molloy, B. B. Hauser, K. L. Effects of Metal Alkoxides on the Lithium Aluminum Hydride Reduction of Substituted Prop-2-ynyl Alcohols J. Chem. Soc., Chem. Commun. 1968, 1017-1019. 

Trialkylboranes may also be used to convert terminal acetylenes into trisubstituted olefins stereospecifically, via the vinyl-lithium reagent generated by Normant s procedure (Scheme 11). The stereochemistry of the product is of... 

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