Compounds unsaturated s. Acetylene

Reduction of a, -unsaturated carbonyl compounds (6, 491 492). The final paper has now been published. In general, )3-5ubstituted cyclohexenones undergo exclusive 1,4-reduction with either Selectride. Acyclic enones generally undergo 1,2-reduction to allylic alcohols. The Selectrides are particularly useful for 1,4-reduction of enoates. Super-Hydride (lithium triethylborohydride) is less useful for this purpose. Unfortunately L-Selectride reduces o./S-acetylenic esters only to propargylic alcohols. 

Addition of HCN to unsaturated compounds is often the easiest and most economical method of making organonitnles. An early synthesis of acrylonitrile involved the addition of HCN to acetylene. The addition of HCN to aldehydes and ketones is readily accompHshed with simple base catalysis, as is the addition of HCN to activated olefins (Michael addition). However, the addition of HCN to unactivated olefins and the regioselective addition to dienes is best accompHshed with a transition-metal catalyst, as illustrated by DuPont s adiponitrile process (6—9). 

Palladium catalysts are more often modified for special selectivities than platinum catalysts. Palladium prepared by reduction of palladium chloride with sodium borohydride Procedure 4, p. 205) is suitable for the reduction of unsaturated aldehydes to saturated aldehydes [i7]. Palladimn on barium sulfate deactivated with sulfur compounds, most frequently the so-called quinoline-5 obtained by boiling quinoline with sulfur [34], is suitable for the Rosenmund reduction [i5] (p. 144). Palladium on calcium carbonate deactivated by lead acetate Lindlar s catalyst) is used for partial hydrogenation of acetylenes to cw-alkenes [36] (p. 44). 

Compounds containing a double or triple bond, usually activated by additional unsaturation (carbonyl, cyano, nitro, phenyl, etc.) in the ap position, add to the 1 4-positions of a conjugated (buta-1 3-diene) system with the formation of a s x-membered ring. The ethylenic or acetylenic compound is known as the dienophile and the second reactant as the diene the product is the adduct. The addition is generally termed the Diels-AIder reaction or the diene synthesis. The product in the case of an ethylenic dienophile is a cyclohexene and in that of an acetylenic dienophile is a cyclohexa-1 4-diene. The active unsaturated portion of the dienophile, or that of the diene, or those in both, may be involved in rings the adduct is then polycyclic. 

The reaction of methylenecyclopropanes with transition metal complexes is well known to promote a catalytic a-ir cycloaddition reaction with unsaturated compounds, in which a trimethylenemethane complex might exist71-76. Recently, much interest has been focused on the interaction of strained silicon-carbon bonds with transition metal complexes. In particular, the reaction of siliranes with acetylene in the presence of transition metal catalysts was extensively investigated by Seyferth s and Ishikawa s groups77-79. In the course of our studies on alkylidenesilirane, we found that palladium catalyzed reaction of Z-79 and E-79 with unsaturated compounds displayed ring expansion reaction modes that depend on the (Z) and (E) regiochemistry of 79 as well as the... 

Aromatic, olefinic, and acetylenic hydrocarbons, but especially saturated hydrocarbons belong to persistent pollutants difficult to eliminate from the troposphere. The only exceptions are some aromatic compounds that undergo direct photodegradation in result of solar irradiation. Alkanes are undoubtedly much less reactive than other organic compounds including unsaturated hydrocarbons, surely because they are more completely saturated and their activation involves cleavage of the relatively strong C—H bond (s = 415 kJ). 

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. 

A polyfunctional organic molecule can contain many different kinds of functional groups, but for nomenclature purposes, we must choose just one suffix. It s not correct to use two sufhxes. Thus, keto ester 3 must be named either as a ketone with an -one. suffix or as an ester with an -oate suffix but can t be named as an -onoate. Similarly, amino alcohol 4 must be named either as an alcohol (-ol) or as an amine i-amine) but can t properly be named as an -olamine. The only exception to this rule is in naming compounds that have double or triple bonds. For example, the unsaturated acid H2C=CHCH2C00H is 3-butenoic acid, and the acetylenic alcohol HCSCCH2CH2CH2CH2OH is 5-hexyn-l-ol. 

Substituted pyridylmethanols 3.72 have been recommended as ligands in nickel-catalyzed 1,4-additions of Et2Zn to a,P-unsaturated carbonyl compounds [112, 972], Asymmetric [2+2+2] cycloadditions of norbomene and acetylenes are catalyzed by a CotyZn/phosphine system and the most efficient ligands are amido-phosphinephosphinites prepared from (S)-valinol 1.60 (R = i-Pr, R = H) [973]. 

Volume 9 deals with the majority of addition and elimination reactions involving aliphatic compounds. Chapter 1 covers electrophilic addition processes, mainly of water, acids and halogens to olefins and acetylenes, and Chapter 2 the addition of unsaturated compounds to each other (the Diels-Alder reaction and other cycloadditions). This is followed by a full discussion of a-, y- and S-eliminations (mainly olefin and alkyne forming) and fragmentation reactions. In Chapter 4 carbene and carbenoid reactions, and in Chapter 5 alkene isomerisation (including prototropic and anionotropic, and Cope and Claisen rearrangements), are discussed. 

A limited number of functionalized acyl silanes have been prepared by the use of 1,3-dithiane methodology as described above, but this route is unfavourable for the synthesis of a, -nnsatnrated acyl silanes . Several /8-hydroxy acyl silanes have, however, been prodnced in high yields using this chemistry acid-catalysed elimination of water from these compounds does give a,/S-unsaturated acyl silanes, and Swem oxidation gives -ketoacyl silanes (Scheme 52). Analogous acetylenic 1,3-dioxanes have been nsed as precnrsors to a, -acetylenic acyl silanes, as have formyl silanes (vide supra. Section III.A.l) ". ... 

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