Triple bonds s. Acetylene derivs

Triple bonds s. Acetylene derivs. Triplet sensitizer -, anthraquinone as - 26,990 Tri-n-propylamine as reagent 26, 66, 564... 

In a manner similar to OsH(OH)(CO)(P Pr3)2, the hydride-metallothiol complex OsH(SH)(CO)(P Pr3)2 adds Lewis bases that are not bulky such as CO and P(OMe)3 to give the corresponding six-coordinate hydride-metallothiol derivatives OsH(SH)(CO)L(P Pr3)2 (L = CO, P(OMe)3). OsH(OH)(CO)(PiPr3)2 and OsH(SH)(CO)(P Pr3 also show a similar behavior toward dimethyl acetylenedi-carboxylate. Treatment of OsH(SH)(CO)(P Pr3)2 with this alkyne affords 6sH SC(C02Me)CHC(OMe)6 (CO)P Pr3)2, which is the result of the tram addition of the S—H bond to the carbon-carbon triple bond of the alkyne. Phenyl-acetylene, in contrast to dimethyl acetylenedicarboxylate, reacts with OsH(SH) (CO)(P Pr3)2 by insertion of the carbon-carbon triple bond into the Os—H bond to give the unsaturated alkenyl-metallothiol derivative Os ( )-CH=CHPh (SH) (CO)(P Pr3 )2, the inorganic counterpart of the organic a, (3-unsaturated mercaptans (Scheme 46).92... 

Many acetylenic acids have been made by the dehydrohalogenation of the dibromo derivatives of olefinic acids. Aliphatic a,/3-acetylenic acids are often decarboxylated under the conditions of the reaction. However, phenylpropiolic acid, C,HsC = CC0,H, and acetylenedicarboxylic acid, HOaCC=CCO,H, are prepared in this way as well as acids having the triple bond in the / y-, y, S-, and more remote positions in the aliphatic chain. 

Generally two main classes of unsaturated sugars in which (1) the anomeric carbon atom is involved in a double bond (glycals) and (2) the unsaturation is placed between other carbon atoms are known. One has to discuss also derivatives with the exo- and enclo-unsaturated bonds (either oleflns/dienes or acetylenes). Another class of unsaturated monosaccharides is represented by the open-chain sugars with the double bond(s) and/or triple bond present in the molecule. The examples of different types of unsaturated sugars are shown in O Fig. 2. Compounds such as glycals will not be discussed here, unless they are used as substrates for the preparation of other, non-anomeric, unsaturated derivatives. 

Ben-Zvi Z. Danon A. Pharmacology of acetylenic derivatives. Chapter 13 in The Chemistry of Triple-Bonded Functional Groups, Suppl. C2, edited by S. Patai, J. Wiley Sons, Chichester, 1994. 

Three important processes have evolved from Reppe s work. Vinylation, the formation of vinyl derivatives by reaction of such compounds as acids, glycols, and alcohols with acetylene, produces the important vinyl esters and vinyl ethers. Ethinylation is defined as the reaction of acetylene with the carbon atom of a reactant without loss of the triple bond. A major application of the ethinylation reaction is to aldehydes and ketones to give alkynols and alkyndiols—e.g., the reaction of acetylene with formaldehyde to give propargyl alcohol and butyn-2-diol-l,4. Carboxylation (also referred to as carbonylation), the reaction of acetylene with carbon monoxide in the presence of metal carbonyls, has been applied to the production of acrylic acid, acrylates, and hydroquinone. 

Acetylenic cobalt complexes greatly facilitate the heterolytic cleavage of adjacent alcohols or ethers. On treatment with Lewis acids, these complexes afford cobalt stabilized carbenium ions, which can be captured by nucleophiles such as enolates. Jacobi and Zheng have employed chiral boron enolates of Evans s oxa-zolidinone 6.91 (R = i-Pr). After removal of the chiral auxiliary, they obtained anti adds 11.43 with a high selectivity [1677] (Figure 11.9). The reaction can be extended to the boron enolates of related oxazolidinones and to a-branched propargyl derivatives. This reaction has been applied to the synthesis of P-aminoacids after Curtius rearrangement and oxidation of the triple bond [1677]. 

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