Alcohols, allylic acetylenic esters

REPPE PROCESS. Any of several processes involving reaction of acetylene (1) with formaldehyde to produce 2-butync-l,4-diol which can be converted to butadiene (2) with formaldehyde under different conditions to produce propargyl alcohol and, form this, allyl alcohol (3) with hydrogen cyanide to yield acrylonitrile (4) with alcohols to give vinyl ethers (5) with amines or phenols to give vinyl derivatives (6) with carbon monoxide and alcohols to give esters of acrylic acid (7) by polymerization to produce cyclooctatetraene and (8) with phenols to make resins. The use of catalysis, pressures up to 30 atm, and special techniques to avoid or contain explosions are important factors in these processes. 

Sato and coworkers have reported an asymmetric synthesis of Baylis-Hillman-type allylic alcohols 48, 49 via a chiral acetylenic ester titanium alkoxide complex (Scheme 9) [41]. These reactions rely on the use of the novel acetylenic ester titanium alkoxide complex 44 with a camphor-derived chiral auxiliary. Optically active, stereodefined hydroxy acrylates 46, 47 were obtained in high yields and with excellent regio- and diastereoselectivities. The chiral auxiliary was subsequently cleaved off by alcoholysis. 

Carbonylation of olefins in the presence of alcohols to give esters is called hydroesterification. Similarly, olefin carbonylation in the presence of carboxylic acids yields acid anhydrides. Both hydroesterification and acid anhydride formation by olefin carbonylation are covered in section 14.6.4. Other carbonylation variations, including the use of acetylenic substrates, thiols and amines as hydrogen sources and the carbonylation of allylic halides are not discussed. Several excellent reviews of hydrocarboxyiation and carbonylation of olefinshave appeared. 

Reaction of Ta-alkyne complexes with R R2C=0. The Ta complexes formed from TaCls/Zn with unsymmetrical alkynes react with carbonyl compounds to form two rcgioisomcric allylic alcohols with a ratio depending on the substituents on the alkync (both steric and electronic effects) as well as the size of the substituents in the carbonyl group. The complexes from acetylenic esters react with carbonyl compounds mainly at the position or to the ester group, whereas complexes from acetylenic amides react mainly at the position fi to the amide. 

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. 

In analogy to allyl halogenides, iodobenzene and other aromatic iodo derivatives can be reacted with Ni(CO)4 and acetylene at reaction temperatures above 100 °C with formation of y-ketoacids or their esters [418, 442], which may be considered as hydrolysis products of p,y-unsaturated y-lac-tones or as hydrogenation products of a,p-unsaturated y-ketoacids or -esters. a,p-Unsaturated y-ketoacids or -esters will be hydrogenated under the reaction conditions, but do not take up carbon monoxide because of the presence of electrophilic substituents. Besides allyl halogenides, allyl alcohols, -ethers and -esters may also be reacted to give unsaturated acids or esters. 

It is also possible to carry out a substrate-controlled reaction with aldehydes in an asymmetric way by starting with an acetylene bearing an optically active ester group, as shown in Eq. 9.8 [22]. The titanium—acetylene complexes derived from silyl propiolates having a camphor-derived auxiliary react with aldehydes with excellent diastereoselectivity. The reaction thus offers a convenient entry to optically active Baylis—Hillman-type allyl alcohols bearing a substituent (3 to the acrylate group, which have hitherto proved difficult to prepare by the Baylis—Hillman reaction itself. 

Another clear example of an acetylene insertion reaction was reported by Chiusoli (15). He observed that allylic halides react catalytically with nickel carbonyl in alcoholic solution, in the presence of CO and acetylene, to form esters of cis-2,5-hexadienoic acid. The intermediate in this reaction is very probably a 7r-allylnickel carbonyl halide, X, which then undergoes acetylene insertion followed by CO insertion and alcoholysis or acyl halide elimination (35). Acetylene is obviously a considerably better inserting group than CO in this reaction since with acetylene and CO, the hexadienoate is the only product, whereas, with only CO, the 3-butenoate ester is formed (15). [See Reaction 59]. 

Acrylic acid [79-10-7] - [AIR POLLUTION] (Vol 1) - [ALDEHYDES] (Vol 1) - [ALLYL ALCOHOL AND MONOALLYL DERIVATIVES] (Vol 2) - [MALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) - [POLYESTERS, UNSATURATED] (Vol 19) - [FLOCCULATING AGENTS] (Vol 11) - [CARBOXYLICACIDS - SURVEY] (Vol 5) -from acetylene [ACETYLENE-DERIVED CHEMICALS] (Vol 1) -from acrolein [ACROLEIN AND DERIVATIVES] (Vol 1) -acrylic esters from [ACRYLIC ESTER P OLYMERS - SURVEY] (Vol 1) -from carbon monoxide [CARBON MONOXIDE] (Vol 5) -C-21 dicarboxylic acids from piCARBOXYLIC ACIDS] (Vol 8) -decomposition product [MAT. ETC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15) -economic data [CARBOXYLIC ACIDS - ECONOMIC ASPECTS] (Vol 5) -ethylene copolymers [IONOMERS] (Vol 14) -in floor polishes [POLISHES] (Vol 19) -in manufacture of ion-exchange resins [ION EXCHANGE] (V ol 14) -in methacrylate copolymers [METHACRYLIC POLYMERS] (Vol 16) -in papermaking [PAPERMAKING ADDITIVES] (Vol 18)... 

Numerous metal-catalyzed reactions of organic halides with carbon monoxide and olefins, acetylenes, aldehydes, etc., have been carried out (21). Only two of these, however, appear to have been developed into generally useful reactions. One is the reaction of allylic halides with carbon monoxide and acetylene in alcoholic solution with a nickel catalyst (22,23). This reaction produces cis-2,5-hexadienoate esters at atmospheric pressure in good yields ... 

Benzyl halides have been reported to react with nickel carbonyl to give both coupling and carbonylation (59). Carbonylation is the principal reaction in polar nonaromatic solvents, giving ethyl phenylacetate in ethanol, and bibenzyl ketone in DMF. The reaction course is probably similar to that of allylic halides. Pentafluorophenyl iodide gives a mixture of coupled product and decafluorobenzophenone. A radical mechanism has been proposed (60). Aromatic iodides are readily carbonylated by nickel carbonyl to give esters in alcoholic solvents or diketones in ethereal solvent (57). Mixtures of carbon monoxide and acetylene react less readily with iodobenzene, and it is only at 320° C and 30 atm pressure that a high yield of benzoyl propionate can be obtained (61). Under the reaction conditions used, the... 

The hydroboration of acetylenes (3) with diisopinocampheylborane (IpC)2BH in THF led after refunctionalisation and transesterification to the olefins (4a, b, c) isolated in good yields. Monooxidation with mCpBA led to the sulfoxide (4d) whereas the sulfone (4e) was obtained with two equivalents of mCpBA. The same sulfone (4e) could also be obtained in an excellent overall yield by radical addition of phenylsulfonyl iodide to the pinacol ester of vinylboronic acid followed by a dehydroiodination in the presence of Et2N (87 % overall yield). The carboxylic ester (4a) could be transformed into the corresponding carboxylic acid (4f) (79 % yield) 11 which led to the acid chloride (4g) by treatment with freshly distilled thionyl chloride at 0°C (91 % yield), p-keto vinylboronates are easily accessible by oxidation of the corresponding protected allylic alcohol according to the following scheme ... 

Air, the cheapest oxidant, is used only rarely without irradiation and without catalysts. Examples of oxidations by air alone are the conversion of aldehydes into carboxylic acids (autoxidation) and the oxidation of acyl-oins to a-diketones. Usually, exposure to light, irradiation with ultraviolet light, or catalysts are needed. Under such circumstances, dehydrogenative coupling in benzylic positions takes place at very mild conditions [7]. In the presence of catalysts, terminal acetylenes are coupled to give diacetylenes [2], and anthracene is oxidized to anthraquinone [3]. Alcohols are converted into aldehydes or ketones with limited amounts of air [4, 5, 6, 7], Air oxidizes esters to keto esters [3], thiols to disulfides [9], and sulfoxides to sulfones [10. In the presence of mercuric bromide and under irradiation, methylene groups in allylic and benzylic positions are oxidized to carbonyls [11]. 

---