5- -3-pentyn

CONDENSATIONS WITH SODAMIDE IN LIQUID AMMONIA Acetylenic compounds are conveniently prepared with the aid of Uquid ammcx as a solvent. The preparation of a simple acetylenic hydrocarbon ( -butylacetylene or 1-hexyne) and also of phenylacetylene is described. Experimental details are also given for two acetylenic carbinols, viz., 1-ethynyl-eyciohoxanul and 4-pentyn-l-ol. It will be noted that the scale is somewhat laige smaller quantities can readily be prepared by obvious modifications of the directions. 

The acetylenic alcohol 4 pentyn-l-ol is conveniently prepared by treatment of tetrahydrofurfuryl chloride with sodamide iu liquid ammonia ... 

Pentyn-l-ol. Prepare a solution of sodamide in liquid ammonia as detailed for n-Butylacetylene. Use a 3-htre three-necked flask, equipped with a Dewar type of reflux condenser (Fig. II, 1, 4, h) cooled with Dry Ice... 

D,L-Arahinitol can be prepared by the action of hydrogen peroxide in the presence of formic acid on divinyl carbinol (36) and, together with ribitol (Fig. ld),fromD,L-erythron-4-pentyne-l,2,3-triol,HOCH2CHOHCHOHC=CH (37). 

Most ring syntheses of this type are of modern origin. The cobalt or rhodium carbonyl catalyzed hydrocarboxylation of unsaturated alcohols, amines or amides provides access to tetrahydrofuranones, pyrrolidones or succinimides, although appreciable amounts of the corresponding six-membered heterocycle may also be formed (Scheme 55a) (73JOM(47)28l). Hydrocarboxylation of 4-pentyn-2-ol with nickel carbonyl yields 3-methylenetetrahy-drofuranone (Scheme 55b). Carbonylation of Schiff bases yields 2-arylphthalimidines (Scheme 55c). The hydroformylation of o-nitrostyrene, subsequent reduction of the nitro group and cyclization leads to the formation of skatole (Scheme 55d) (81CC82). 

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]. 

Pentyn-1-ol, 33, 68 Peracetic acid, 33, 79 -Phenetidine hydrochloride, 31, 11 a-Phenoxyacetoacetic acid, 33, 44 Phenylacetamide, 32, 92 Phenylacetic acid, 32, 93, 94 33, 70 imino ether hydrochloride, 32, 94 N-Phenylacetimidochloride, 31, 51 Phenylacetonitrile, 30, 44 32, 92 Phenylacetylene, 30, 72 7-Phenylallylsuccinic acid, 31, 85 7-Phenylallylsuccinic anhydride, 31, 86 Phenylazide, 31,16 Phenylazoacetoacetic acid, 32, 85 Phenyl benzoate, 32, 103 IttZtti-l-PHENYL-l,3-BUTADIENE, 30, 75 7-Phenylbutyric acid, 33, 91 a-PHENYL-a-CARBETHOXYGLUTARO-NITRILE, 30, 80, 82 tt-Phenylcinnamonitrile, 32, 63 Phenyldichlorophosphine, 31, 88 0-PhENYLENE CARBONATE, 33, 74 o-Phenylenediamine, 30, 56, 86... 

Pentyn-l-ol has been prepared from 4-penten-l-ol3 by bromi-nation followed by dehydrobromination with alkali,7 by the reaction of 3-bromodihydropyran with w-butylsodium or w-butyl-lithium,6 8 by the reaction of 2-methylenetetrahydrofuran with w-amylsodium or w-butyllithium,8 and by the method used in this preparation.9... 

The dinuclear isonitrile and alkoxycarbene complexes 6 and 7 were obtained from [Fe(CO)3( X-dppm) Tl2- j,2-Si(OMe)2(OMe))PtCl] by chloride substitution with isonitriles and 3-butyne-l-ol (or ( )-4-pentyne-2-ol), respectively [2], In these complexes, the organic ligand bound to Pt only occupies one coordination site, thus allowing the trimethoxysilyl ligand to display a T 2- i2-Si-0 bonding mode. 

Preparation of 4-pentyn-l-ol from 3-bromo-1-propanol and sodium acetylide ... 

Allenyldibromoborane was obtained in 34% yield by the reaction of boron tribromide with allenyltributylstannane below -80 °C [28], Allenyldimethylborane was likewise prepared in 84% yield from dimethylboron bromide. In neither case was the propargylborane observed. Both allenylboranes react with acetone to yield 2-methyl-4-pentyn-2-ol after hydrolysis (Eq. 9.25). 

The above-mentioned iridium complex, C4, as well as [ lr[bis(l-methylimidazol-2-yl)methane (CO)2][BPh4] (C5), also appeared very efficient in a one-pot tandem hydroamination/hydrosilylation reaction of 4-pentyn-l-amine with HSiEts to form 2-methylpyrroline, and then subsequently l-(triethylsilyl)-2-methylpyrrohdine with an essentially quantitative yield (Equation 14.5) [54]. 

In 2002, Musaev and coworkers performed the first theoretical investigation of the mechanism with the aid of density functional theory calculations [26]. They first studied the mechanism of cycloisomerization in the absence of a tungsten catalyst, as shown in Scheme 4.14. The D FT calculations showed that the exo-cycloisomerization of 4-pentyn-l-ol via a concerted transition state leading to a five-membered-ring exo product had a high barrier (52.0 kcalmol ) (path a of Scheme 4.14). The pathways leading to a six-membered-ring endo product have also been calculated (paths b and c... 

With a tungsten pentacarbonyl catalyst, the calculated mechanisms are summarized in Scheme 4.15 [26]. Coordination of the 4-pentyn-l-ol substrate to the pentacarbonyl tungsten leads to the formation of the 7i-alkyne-W(CO)5 adduct Wl. This coordination process was calculated to be exothermic by 24.3 kcal mol. The cydoisomerization leading to a five-membered-ring exo product starts with the 7i-complex Wl via a one-step process with a barrier of 46.5 kcal mol (path a of Scheme 4.15). The barrier calculated here is comparable with that calculated for the catalyst-free process. From Wl to W3, the tungsten metal center does not play a significant role in the isomerization process. 

In path a (Scheme 4.15), the barrier for the rate-determining step is 46.5 kcal mol. In path b2 (Scheme 4.15), the barrier for the rate-determining step (the alkyne-to-vinylidene tautomerization) is only 26.4kcal mol . The significant barrier difference (about 20 kcal mol ) between paths a and b2 explains the endo-regioselectivity observed experimentally in the cydoisomerization of 4-pentyn-l-ol [117, 118]. 

Although silylformylation of 3-butyn-I-ol 84 gives normal product 85 preferentially in the absence of EtsN, an appreciable amount (38%) of 7-lactone 86 is formed concomitantly." Protection of the hydroxy group in 84 leads to selective silylformylation of the acetylenic moiety as shown in Scheme 3. Hydrolysis of the silyl ether in 88 gives 85 as a single product. 4-Pentyn-I-ol 89 reacts with Mc2PhSiH under CO pressure to give a mixture of silylformylation product 90 (20%) and (5-lactone 91 (38%) after a short reaction time (0.5 h) (Equation (16)). The unusual lactone formation is not observed in the reaction of 5-hexyn-l-ol 92 in the presence of EtsN (Equation (17)). ... 

Radical carbonylation reaction serves as a powerful tool for the synthesis of a range of carbonyl compounds. Radical carbonylation has been successfully applied to the synthesis of functionalized ketones from alkyl, aryl, and alkenyl halides.The radical aminocarbonylation reaction of alkynes and azaenynes provided efficient routes to 2-substituted acrylamides, lactams, and pyrrolidinones. For example, the aminocarbonylation of 4-pentyn-l-yl acetate 318 initiated by tributyltin hydride (Bu"3SnH) (30mol%) with AIBN (20mol%) gave acrylamide 325 in 92% yield (Scheme 43).A proposed mechanism starts from the addition of tributyltin radical 319 to alkyne... 

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