3-Methyl-4-pentyn

Property Hexynol Ethyl-octynol Methyl-butynol Methyl-pentyn... 

Property7 Hexynol Ediyl-octynol Mediyl-butynol Methyl-pentyn ol... 

In the sedative-hypnotic series, most of the acetylenic alcohols are used as carbamic esters meparfynol, ethinamate, etc. The bromoethynyl moiety confers an acidity comparable to that induced by a trichloromethyl group (compare for example chlorobutanol with 3-methyl-pentyne-3-ol). Bromoethynylcyclohexanol is sufficiently acidic to form salts its bismuth salt was used for a while as an antisyphilitic drug under the name of biarsamide. In the steroid series the metabolism of the ethynyl group can lead (by hydration of the triple bond) to 17 a-methylketones. 

Hydroxy-2-methyl- pentyne-4 a-Methylene-y-dimethyl-Y-butyro- lactone 7.4 [429]... 

Recently, the already-known polymers of (5)-3-methyl-pentyne and (5 )-4-methyl-l-hexyne [27, 28] as well as of (5)-5-methyl-l-heptyne, (iS)-6-methyl-l-octyne and (S )-3,4-dimethylpentyne (Xlla—e) have been prepared in the presence of iron tris(acetylacetonate)-aluminum triisobutyl catalyst [29]. 

To a mixture of 50 ml of dry THF and 0.050 mol of l-tert.-butoxy-2-pentyne (prepared by ethylation of HC-CCH O-tert.-Ci,H9 in liquid ammonia was added 0.055 mol of butyilithium in about 35 ml of hexane in 10 min at -30°C. After stirring for 20 min at -25°C the solution was cooled to -50°C and 0.06 mol of methyl iodide was added in one portion, followed 10 min later by 50 ml of water. The aqueous layer was separated and extracted twice with diethyl ether. The solutions were dried over magnesium sulfate and concentrated in a water-pump vacuum. 

The alkane formed by hydrogenation of (S) 4 methyl 1 hexyne is optically active but the one formed by hydrogenation of (S) 3 methyl 1 pentyne is not Explain Would you expect the products of hydrogenation of these two compounds in the presence of Lindlar palladium to be optically active" ... 

Assume that you need to prepare 4 methyl 2 pentyne and discover that the only alkynes on hand are acetylene and propyne You also have available methyl iodide isopropyl bromide and 1 1 dichloro 3 methylbutane Which of these compounds would you choose in order to perform your synthesis and how would you carry it out" ... 

CHsCHjCHzC CH (1 pentyne) CHsCHjC CCHs (2 pentyne) (CH3)2CHC=CH (3 methyl 1 butyne)... 

Dimethylfuran, in a sensitized reaction, gave 1,3-dimethylcyclopropene (the main product), isoprene, cis- and rran.s-l,3-pentadiene, 2-pentyne, and 1-methylcyclopropenyl methyl ketone (Scheme 7) (70JPC574) the ring contraction showed a high selectivity. 

The irradiation of 2,5-dimethylfuran in the presence of mercury vapor gave a complex mixture of products. Carbon monoxide and propene were removed as gaseous products. Then, cis- and rran.s-l,3-pentadiene, isoprene, 1,3-dimethylcyclopropene, 2-pentyne, 2-ethyl-5-methylfuran, hexa-3,4-dien-2-one, 1-methyl-3-acetylcyclopropene, and 4-methylcyclopent-2-enone were obtained (Scheme 8) (68JA2720 70JA1824). The most abundantproduct was the cyclopentenone 19, the second was the 1,3-pentadiene 12, while the third product was the cyclopropenyl derivative 18. 

Hexyne, 2-hexyne, 3-hexyne, 3-methyl-Hpentyne, 4-methyl-l-pentynep 4-methyl-2-pentyne, 3.3-dimethyl-l-butyne... 

The Rh and Ir complexes 85-88 (Fig. 2.14) have been tested for the intramolecular hydroamination/cyclisation of 4-pentyn-l-amine to 2-methyl-1-pyrroline (n = 1). The reactions were carried out at 60°C (1-1.5 mol%) in THF or CDCI3 The analogous rhodium systems were more active. Furthermore, the activity of 87 is higher than 85 under the same conditions, which was attributed to the hemilabihty of the P donor in the former complex, or to differences in the trans-eSects of the phosphine and NHC ligands, which may increase the lability of the coordinated CO in the pre-catalyst [75,76]. 

With terminal alkynes, the direction of the reaction depends on the nature of the substituent, the type of amine and the catalyst. Thus, dialkylamines can react with propyne to give 4-dialkylamino-4-methyl-2-pentynes traced from the Hy regioselec-hve formation of 2-dialkylaminopropene, i.e. the Markovnikov hydroaminahon product (Scheme 4-11) [256]. 

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