Dienes from acetylenes

Phosphonic acid esters from chlorophosphites— 1,3-Dienes from acetylene derivatives s. 19, 725... 

A 50-60%-soln. of N,N-diethylprop-2-ynylamine in hexane passed al 65° during ca. 40 min. through a KNHa-on-alumina catalyst N,N-diethylprop-l-ynyl-amine. Y 65%. F. e. s. A. J. Hubert and H. G. Viehe, Soc. (G) 1968, 228 enamines from 2-ethyleneamines s. Soc. (G) 1968, 2048 1,3-dienes from acetylene derivatives, also conjugated tetraenes from a,co-diynes, s. Ghem. Ind. 1968, 975. 

Feedstocks come mainly from catalytic cracking. The catalyst system is sensitive to contaminants such as dienes and acetylenes or polar compounds such as water, oxygenates, basic nitrogen, organic sulfur, and chlorinated compounds, which usually require upstream treatment. 

The first stage does the bulk of the separation, and the second is used to remove other dienes and acetylenes from the isoprene. In the extractive distillation tower of each stage, the ACN solvent is introduced near the top, and being the highest boiling component, travels downward. The effective relative volatility of the less unsaturated hydrocarbons is increased with respect to isoprene. Thus most of the impurities go overhead and the isoprene is carried down with the solvent. 

Enyne metathesis starting either from acetylenic boronates and homoallylic alcohols [104a,c] or from propargyl alcohols and allylboronates [104b] has recently been described. The resulting boronated dienes can be converted to allenes or cycloaddition products. The cross metathesis of vinylcyclopropyl-boronates directed toward the total synthesis of natural products has very recently been investigated by Pietruszka et al. [104d]. 

The various products obtained from acetylenic diols 54 in the presence of acids suggest the formation and interconversion of acetylene-allene-diene cationoid intermediates (equation 18)33. The allene intermediates can be sometimes isolated and they were reported as participants in the acid-catalyzed reactions of alkynylpyrylium salts 55, a driving force of which is an aromatization of the pyrane ring (equations 19-21)34,35. 

Polydienes. The most important diene homopolymers are polybutadiene and polyisoprene produced by anionic or coordination polymerization.184,186,187,487 189 Highly purified starting materials free from acetylenes, oxygen, and sulfur compounds are required. 

Conjugated dienes are much less common in cuticular lipids, and there are a large number of ways in which any desired isomer can be made with high stereoselectivity. The interested reader is referred to the compilation of methods in Mori (1992) as a starting point. A convenient route to any one or all four stereoisomers of a conjugated diene from two acetylenic precursors has been described by Svatos and Saman (1997). 

In aromatic hydrocarbons, some substituted alkenes, dienes, substituted acetylenes and ketones, one half of the n orbitals are empty and an electron can easily be placed in these antibonding orbitals. The capture of an electron by the acceptor molecule is an exothermic process because the energy of the antibonding orbitals lies below the level of the ionization potential of the acceptor radical anion. Many radical anions formed from unsaturated molecules are themselves stable they do not decompose and may exist indefinitely under suitable experimental conditions [182a],On the other hand, they react easily with other molecules. 

Refinery LPG, typically produced from a fluid cat-cracker unit, contains in addition to paraffins a large amount of olefins particularly propylene and isobutene. These olefins and isobutane have refinery uses and are often used in producing additional fuel such as polymer gasoline and alkylate. Also present are trace quantities of dienes and acetylenes. 

The product gases are cooled and compressed (4) to facilitate separation of products and by-products. The suction-side of the compressor ensures that upstream units operate at a low pressure. The product gases are first dried (5) and the cooled product passed to a cryogenic separator (6) which removes hydrogen from the system. Some is recycled with the other portion passed-on for other uses. A selective hydrogenation unit (7) removes dienes and acetylenes. A final distillation train removes light hydrocarbon (C2-), propylene product, propane, which is recycled, and a C4 by-product. 

Many other addition reactions of olefins, dienes, and acetylenes are known, which are catalyzed by metal carbonyls including Ni(CO)4, Fe(CO)5, and Co2(CO)8 and by carbonyl derivatives such as hydrocarbonyls or phosphine-substituted carbonyls. Among these are the hydro-carboxylation, hydroesterification, and hydrocyanation of olefins the synthesis of hydroquiniones from acetylenes, carbon monoxide, and water ... 

O. R. XIII-3, C. Walling, and E. S. Huyser, Free Radical Additions to Olefins and Acetylenes to Form Carbon-Carbon Bonds XI11-1, G. Zweifel and H. C. Brown, Hydration of Olefins, Dienes, and Acetylenes via Hydroboration XIII-2, W. E. Parham and E. E. Schweizer, Halocyclopropanes from Halocarbenes. ... 

Under controlled conditions, divinylcuprates derived from acetylene carbocupration can be converted to the (IZ, 3Z)-bis(dienyl)cuprates using an excess of acetylene. Reacting the divinylcopper intermediates with electrophiles affords conjugated (Z, Z)-dienes in a highly stereoselective manner." ... 

The carbon content of the poisoned samples (self-poisoning and deliberate poisoning at T>373 K in diene or acetylene) was measured by TPO (1.3 kPa O2, flow and/or static systems, respectively CO2 (m/z=44) and CO (m/z=28) were detected by mass spectrometer (AEI MS 20 and Balzers QMG 511). DSC thermograms (Perkin Elmer DSC-4) were recorded in O2 stream (40 K/min ramp from ambient to 773 K). 

Data on the formation of carbonaceous materials from diene and acetylene over 373 K and selectivity of n-butane in butadiene hydrogenation (H2/BD=2.2, 1.33 kPa BD, 284 K) are collected in Table 3. The hydrogen content of the deposits was calculated from the amount of the self-hydrogenated products in the gas phase. Reaction of 1,3-butadiene was accompanied with formation of n-butenes whereas in reaction of acetylene 1,3-butadiene was the principal product. Hydrogen content of the deposits was also measured by TPD technique. Desorption of H2 is presented in Figure 3 measured on Cat. C before (1) and after BD poisoning at 489 K for 18 hr (2). 

Formation of fused heterocycles from acetylenic or allenic sulfones and pyrroles or furans as dienes 01T5263. 

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