Reactions of Acetylenes and Olefins

The absolute stereochemical selectivities achieved in these reactions can be explained in terms of the nnf/-exo-transition-state models 16, 17, and 18, which are analogous to those previously proposed for the reaction of dienes and olefinic dienophiles (Fig. 8) [12,27d]. These transition-state models are based on three assumptions (i) the substituent in the chiral ligand blocks the same enantiofacial side of the carbonyl in the Diels-Alder reactions of acetylenic and olefinic aldehydes (ii) exo-transition structures predominate and (hi) anh-coordination of the bulky chiral Lewis acid to carbonyl is preferred in the transition state. 

Carbonylation reactions of acetylenes and olefins are used in the preparation of acids, esters, amides, and other compounds ... 

Garboxylation Reaction. The carboxylation reaction represents the conversion of acetylene and olefins into carboxyHc acids (qv) or their derivatives. The industrially important Reppe process is used in the synthesis of P-unsaturated esters from acetylene. Nickel carbonyl is the catalyst of choice (134). 

Acetylenes have hijh synthetic utility, and hydrogenation of the triple bond occurs in many reaction sequences (7). Often the goal of this reduction is formation of the cis olefin, which usually can be achieved in very high yields (for an exception, see Ref. 10). Continued reduction gives the paraffin. Experimentally, both the relative and absolute rates of acetylene and olefin hydrogenation have been found to depend on the catalyst, substrate, solvent, reaction conditions, and hydrogen availability at the catalyst surface. Despite these complexities, high yields of desired product usually can be obtained without difficulty. 

From among the variety of non-carbohydrate precursors, acetylenes and alkenes have found wide application as substrates for the synthesis of monosaccharides. Although introduction of more than three chiral centers having the desired, relative stereochemistry into acyclic compounds containing multiple bonds is usually difficult, the availability of such compounds, as well as the choice of methods accessible for their functionalization, make them convenient starting-substances for the synthesis. In this Section is given an outline of all of the synthetic methods that have been utilized for the conversion of acetylenic and olefinic precursors into carbohydrates. Only reactions leading from dialkenes to hexitols are omitted, as they have already been described in this Series.7... 

To investigate the oxidative addition of acyl halides to a metal to form the acyl complex and to find a better decarbonylation agent, we selected chlorotris(triphenylphosphine) rhodium (XI) as a model complex. This complex is known to catalyze the oxo reaction (8) and the homogeneous hydrogenation of acetylenes and olefins (7, 28). 

Jonas and Tadic [71] have investigated the homogeneous cobalt-catalyzed co-cyclotrimerization of acetylene and olefins. The reaction with -Ind-cobalt bis(ethylene) as the catalyst was carried out with ethylene, a-olefins and 2-butene as well as cyclohexene and cyclooctene (eq. (25)). 

Katz, T. J. Reactions of acetylenes and alkenes induced by catalysts of olefin metathesis. NATO ASI Ser., Ser. C1989, 269, 293-304. 

Topics of this section include 1,2-insertion reactions of acetylenes (b), olefins (c), allenes (d), oxygen (e), carbon dioxide (f), sulfur dioxide (g), sulfur trioxide (h), and nitric oxide (i). 

Insertion Reactions into Element-Halogen Bonds 11.6.2. Insertions of Acetylenes and Olefins... 

Risse and S. Breunig, Transition metal catalyzed vinyl addition polymerizations of norbor nene derivatives with ester groups, Makromol. Chem. 193, 2915 (1992) C. Mehler and M. Risse, Addition polymerization of norbornene catalyzed by palladium(2- -) compounds. A polymerization reaction with rare chain transfer and chain termination, Macromol. 25, 4226 4228 (1992) R.G. Schulz, Polym. Lett. 4, 541 (1966). C. Tanielian, A. Kiennemann, and T. Osparpucu, Influence de differents catalyseurs abase d elements de transition du groupe VIII sur lapol3mierisation du norbor nene, Can. J. Chem. 57, 2022 (1979) A. Sen and T. W. Lai, Catalytic polymerization of acetylenes and olefins by tetrakis(acetonitrile)palladium(II) ditetrafluoroborate, Organometallics 1, 415 (1982) C. Mehler and W. Risse, Pd(II) catalyzed polymerization of norbornene derivatives, Mak romol. Chem. Rapid Commun. 12, 255 (1991). 

Meso-lonlc Thiazolo[2,3-6]thiazoles.—Thiazoline-2-thione (179) reacts readily with 2-bromo-2-phenyIacetyl chloride in the presence of base (Scheme 16) to produce 2-phenylthiazolo[2,3-6]thiazolium-3-olate (180), which undergoes cycloaddition reactions with acetylenic and olefinic dipolarophiles in much the same way as (175). With dimethyl acetylenedicarboxylate, for example, the thiazolo(3,2-a]pyridin-5-one (181) is formed. ... 

Addition reactions of ArS to alkynes produce cis- and trans-olefins, which seem to be controlled kinetically [42]. To understand stereospecific addition processes, kinetic studies are important. Some representative data obtained by the flash photolysis method are shown in Table 5 [36]. For each pair of acetylene and olefins (Scheme 8), the slopes of the Hammett plots for the rate constants with different substituents in ArS do not vary much, suggesting that the reactivities of these acetylenes and olefins are mainly determined by the resonance stability of the transition state of the reaction, but not by the polar nature of the transition state. Thus, the resonance stability of the C atom-centered radicals in... 

This observation may well explain the considerable difference between metal-olefin and metal-acetylene chemistry observed for the trinuclear metal carbonyl compounds of this group. As with iron, ruthenium and osmium have an extensive and rich chemistry, with acetylenic complexes involving in many instances polymerization reactions, and, as noted above for both ruthenium and osmium trinuclear carbonyl derivatives, olefin addition normally occurs with interaction at one olefin center. The main metal-ligand framework is often the same for both acetylene and olefin adducts, and differs in that, for the olefin complexes, two metal-hydrogen bonds are formed by transfer of hydrogen from the olefin. The steric requirements of these two edgebridging hydrogen atoms appear to be considerable and may reduce the tendency for the addition of the second olefin molecule to the metal cluster unit and hence restrict the equivalent chemistry to that observed for the acetylene derivatives. 

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