1- -l-propyne

A suspension of 0.35 mol of sodium amide in 400 ml of liquid ammonia was prepared in the usual way (e./. Chapter II, Exp. 11) (note 1). To this suspension was added with swirling 0.30 mol of 1-methylthio-l-propyne, in portions of about 10 g, waiting about 10 s after the addition of each portion. Swirling was continued for 1.5 min after the addition of the last portion. Immediately thereafter the... 

To a mixture of 65 ml of dry benzene and 0.10 mol of freshly distilled NN-di-ethylamino-l-propyne were added 3 drops of BFa.ether and 0.12 mol of dry propargyl alcohol was added to the reddish solution in 5 min. The temperature rose in 5-10 min to about 45°C, remained at this level for about 10 min and then began to drop. The mixture was warmed to 60°C, whereupon the exothermic reaction made the temperature rise in a few minutes to B5 c. This level was maintained by occasional cooling. After the exothermic reaction (3,3-sigmatropic rearrangement) had subsided, the mixture was heated for an additional 10 min at 80°C and the benzene was then removed in a water-pump vacuum. The red residue was practically pure acid amide... 

A mixture of 0.10 mol of 1-ethylthio-l-propyne (see IV, Exp. 23 and Ref. 1) and 100 ml of glacial acetic acid was heated at 95°C, then 35 ml of 33% hydrogen peroxide were added in 15 min with occasional cooling. After this addition the mixture was kept for 1 h at 100°C, then cooled to 20°C and 200 ml of water were added. Ten extractions with 20-ml portions of chloroform were carried out and the combined extracts were dried over magnesium sulfate (without previous washing)... 

Alkynes with EWGs are poor substrates for the coupling with halides. Therefore, instead of the inactive propynoate, triethyl orthopropynoate (350) is used for the coupling with aryl halides to prepare the arylpropynoate 351. The coupling product 353 of 3,3-dicthoxy-l-propyne (352) with an aryl halide is the precursor of an alkynal[260]. The coupling of ethoxy) tributylstan-nyl)acetylene (354) with aryl halides is a good synthetic method for the aryl-acetate 355[261]. 

Methylisoxazole (297 R = Me) and its homologs can be synthesized by reaction of hydroxylamine hydrochloride with 1-alkyl-3-dimethylamino-2-propen-l-one (296) (54IZV47), the anilino derivatives of acetoacetaldehyde (47G556), 3-dimethyl-aminomethylene-l-propyne (equation 7) (69ZOR1179) and the /3-ketoaldehyde (293) (66JOC3193). 

Scheme 8 summarizes the construction of the requisite building blocks 40, 41, and 50. Alkylation of the lithio derivative of l-(tri-methylsilyl)-3-phenylthio-l-propyne (42) with 3-iodo-l-(tert-butyl-dimethylsilyloxy)propane in the presence of HMPA affords compound 43 in 90% yield. Selective desilylation of the protected alcohol is achieved by warming 43 to 40 °C in ACOH-THF-H2O... 

Propargyl Bromide (3-Bromo-l-propyne). HC=CCH2Br mw 118.97 colorl to faintly brownish liq mp 24.4° bp 88—90° d 1.52 g/cc RI 1.4320 at 20°. Sol in ale, eth, benz chlf. Flammable flash pt 10° (closed), 18° (open) ignition temp 328° lower flammable limit 3.0%. It can be decompd by mild shock. When heated under confinement, it decomps with expl violence and may detonate. When suitably diluted, as with 20—30% by wt of toluene, its expl properties are practically eliminated (Ref 4)... 

Ethyleneimine reacts with (p-tolylsulfonyl)acetylene to give only the (Z)-product 115 via trans addition (equation 91), while primary and secondary aliphatic amines afford ( )-products76. With nonterminal acetylenes such as l-(ethylsulfonyl)-l-propyne, the reactions of ethyleneimine, n-propylamine and f-butylamine give mixtures of ( )- and (Z)-adducts. The double conjugate addition of sodium sulfide, selenide and telluride to bis(l-propynyl)sulfone (116) produces heterocycles (117) as illustrated in equation 9277. 

Addition of zirconocene to unsymmetric acetylenes is often regiospe-cific. Thus the reaction of 1-trimethylsilyl-l-propyne (50) with zirconocene dichloride and magnesium amalgam gives the zirconocycle 51, where the large trimethylsilyl groups are adjacent to zirconium.21 Iodination of 51 affords diiodide 52, which has been converted to the corresponding di-stibaferrocene 55 and dibismaferrocene 56. 

Dipolar cycloaddition of pyrido[2,l-A][l,3]thiazinium betaine 507 (R = Me) with 1-diethylamino-l-propyne afforded cycloadduct 508, from which quinolizin-4-one 509 formed by a rapid cheletropic extrusion of COS (Scheme 53) <1995T6651>. 1,4-Dipolar cycloaddition of 507 and 4-phenyl-l,2,4-triazoline-3,5-dione yielded 511 (via 510) <1995H(41)1631> and 512 <1995T6651>. 

The cycloaddition of Weinreb amide functionalized nitrile oxide with a range of dipolarophiles has been studied. N-Methoxy-N-methylcarbonocyanidic amide, nitrile oxide 207 (i.e., a nitrile oxide of Weinreb amide type derivative) was generated from 2-chloro-2-(hydroxyimino)-N-methoxy-N-methylacetamide as intermediate and used in situ. Thus, addition of 3-bromo-l-propyne as dipolarophile to this precursor of 207, followed by quenching with triethylamine, gave 5-(bromo-methyl)-N-(methoxy)-N-methyl-3-isoxazolecarboxamide 208 in 55% to 60% yield (367). 

Syntheses of l-aryl-3,3,3-trilluoro-l-propynes and their reactions with nitrile oxides to give 3,5-diaryl-4-tri(luoromethylisoxazoles have been carried out. In particular, l-(4-chlorophenyl)-3,3,3-trilluoro-l-propyne, on reaction with 4-chlorobenzohydroximoyl chloride in the presence of Et3N in PhMe, give a 45% mixture of 211 (R = R1 = 4-CIC6H4) and the regioisomer 212 in the ratio of 97 3, respectively (370). 

The Lewis acid catalyzed thermal [2 + 2] cycloaddition between 1-cyano-cyclopentene (68) and l-(N,N-diethylamino)-l-propyne (69) afforded the enamine... 

In the course of investigation of reactivity of the mesoionic compound 44 (Scheme 2) the question arose if this bicyclic system participates in Diels-Alder reactions as an electron-rich or an electron-poor component <1999T13703>. The energy level of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) orbitals were calculated by PM3 method. Comparison of these values with those of two different dienophiles (dimethyl acetylenedicarboxylate (DMAD) and 1,1-diethylamino-l-propyne) suggested that a faster cycloaddition can be expected with the electron-rich ynamine, that is, the Diels-Alder reaction of inverse electron demand is preferred. The experimental results seemed to support this assumption. 

An exceptional approach to phosphorus-substituted alkoxyallenes via isomerization of alkynes was introduced by Beletskaya s group. The treatment of 1-alkoxy-l-propynes 23 with l-halo-2,2-bis(trimethylsilyl)phosphaethen 24 furnished alkoxyallenes 25 (Scheme 8.9) [31]. 

Trialkyl- or triarylallenyltin compounds can also be prepared by Sn2 displacement of propargylic mesylates with various stannylcopper reagents in THF (Eq. 9.82) [71]. This reaction is postulated to proceed by an anti Sn2 pathway based on the stereochemical relationship between the enantioenriched mesylate and the allenic product (Eq. 9.83). The allene obtained from the reaction of the mesylate of (R)-3-phenyl-l-propyn-3-ol with Ph3SnCu was assigned the (P) configuration from a consideration of the observed optical rotation and an application of Brewster s rules [71]. 

Electrophilic addition of PhI(OAc)2 to 1,2-allenyl ether led to the formation of 3-acetoxy-3-alkoxy-l-propyne [51]. 

Bromo-l-propyne, see Propyne Bromoxynil, see Bromoxvnil octanoate y-BTC, see Eindane... 

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