Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Dimethyl propargyl

Dimethyl propargyl alcohol 95 serves as a mask for the corresponding terminal acetylene. Therefore, basic cleavage of 95 unveiled the terminal acetylene, which was coupled in situ with 2-bromobenzothiazole in the presence of a phase-transfer catalyst to afford the unsymmetrical diarylbutadiyne 96 [53],... [Pg.314]

Moderate the nitrogen flow, remove the septum, and put Pd2(dba)3 CHCl3 (158 mg, 0.153 mmol), dppe (0.243 g, 0.61 mmol), and dimethyl propargyl malonate (1.24 g, 7.32 mmol) into the Schlenk tube. [Pg.56]

Aconitatc was obtained as a minor product in the carbonylation of propar-gyl alcohol[479]. However, in the two-step synthesis of methyl aconitate (536) from propargyl alcohol in 70% overall yield, the first step is the oxidative carbonylation under CO and air using Pdli and KI to giNe dimethyl hydro-xymethylbutenedioate (535), which is carbonylated further to give trimethyl aconitate (536) by u.sc of [Pd(Tu)4jl2 as a catalyst[480]. [Pg.99]

As an application of maleate formation, the carbonylation of silylated 3-butyn-l-ol affords the 7-butyrolactone 539[482], Oxidative carbonylation is possible via mercuration of alkynes and subsequent Lransmetallation with Pd(II) under a CO atmosphere. For example, chloromercuration of propargyl alcohol and treatment with PdCF (1 equiv.) under 1 atm of CO in THF produced the /3-chlorobutenolide 540 in 96% yield[483]. Dimethyl phenylinale-ate is obtained by the reaction of phenylacetylene, CO, PdCU, and HgCl2 in MeOH[484,485]. [Pg.100]

The procedure described is that of Wille and Saffer. Propiolaldehyde has also been prepared by the oxidation of propargyl alcohol using ammonium dichromate or manganese dioxide in 10% sulfuric acid. Propiolaldehyde has also been prepared by warming the dimethyl or diethyl acetal with dilute sulfuric acid. ... [Pg.68]

A second, more convenient approach was tried starting with dicyclopropyla-cetylene 56 [15-17] which, after deprotonation with tert-butyllithium at both propargylic positions, yielded the bisaldehyde 57 upon treatment with dimethyl-formamide. The latter was converted to the bis(dibromoethenyl) derivative 58, and this in turn to the dibromotriyne 59 by standard methods (Scheme 11) [18]. The dibromide 59 was coupled with the ethynylcyclopropylheterocuprate 50 to give the terminally bis-protected pentayne 60. [Pg.9]

However, the classical version of the ABAC, when triallyl-, trimethallyl-, or tricrotylborane are involved in the reaction with RR1CHC=CH (e.g., propargylic ethers), can be applied only for the synthesis of 1-boraadamantane derivatives 35, 3,5-dimethyl- 36 and 4,6-dimethyl-l-boraadamantanes 37 (Scheme 7). Hence, the stmctures of the final cage compounds are rigidly restricted by the stmctures of the starting allylic boranes. [Pg.586]

Propargyl alcohol, 36, 67 Propiolaldehyde, 36, 66 Propionic acid, /3,/3 -thiodi-, dimethyl ester, 30, 65... [Pg.53]

Scheme 2.7 Influence of dimethyl sulfide on the Sn2 substitution of propargyl oxirane 20. Scheme 2.7 Influence of dimethyl sulfide on the Sn2 substitution of propargyl oxirane 20.
The effectiveness of dimethyl sulfide as an additive for the selective formation of anti-product 22 from propargyl epoxide 20 may be due to the formation of stabilized copper species, which are less prone to undergo electron transfer processes. In this respect, other soft ligands which bind strongly to copper, in particular phosphines and phosphites [8h-j, 25, 28], have been used even more frequently. These additives also serve to suppress the formation of a common side product, i.e. an allene containing a hydrogen atom instead of the carbon substituent which should... [Pg.55]

The beneficial effect of added phosphine on the chemo- and stereoselectivity of the Sn2 substitution of propargyl oxiranes is demonstrated in the reaction of substrate 27 with lithium dimethylcyanocuprate in diethyl ether (Scheme 2.9). In the absence of the phosphine ligand, reduction of the substrate prevailed and attempts to shift the product ratio in favor of 29 by addition of methyl iodide (which should alkylate the presumable intermediate 24 [8k]) had almost no effect. In contrast, the desired substitution product 29 was formed with good chemo- and anti-stereoselectivity when tri-n-butylphosphine was present in the reaction mixture [25, 31]. Interestingly, this effect is strongly solvent dependent, since a complex product mixture was formed when THF was used instead of diethyl ether. With sulfur-containing copper sources such as copper bromide-dimethyl sulfide complex or copper 2-thiophenecarboxylate, however, addition of the phosphine caused the opposite effect, i.e. exclusive formation of the reduced allene 28. Hence the course and outcome of the SN2 substitution show a rather complex dependence on the reaction partners and conditions, which needs to be further elucidated. [Pg.56]

The classical examples of these two routes are the conversion of 2,5-dimethyl-2,4-hexadiene (113) via the bisdibromocarbene adduct 114 into the terminally fully methylated bisallene 115 (Scheme 5.15) [43] and the reductive coupling of propargyl bromide (116). [Pg.199]

The propargyl alcohol 316 reacts with carbon dioxide and aliphatic or aromatic primary amines RNH2 under tributylphosphine catalysis to yield 5,5-dimethyl-4-methylene-oxazolidin-2-ones 317374. [Pg.598]

The present method is practical and efficient as it employs readily available enantioenriched propargylic alcohols as precursors to the allenylindium reagents. With achiral aldehydes the diastereoselectivity is high for branched aldehydes, moderate for unbranched aldehydes, and low for benzaldehyde (Table I). With cHral a-methyl aldehydes the additions proceed under effective reagent control to afford anti adducts of high ee and with excellent diastereoselectivity (eq. 1 and 2). Comparable results were obtained with 3 1 dimethyl sulfoxide-tetrahydrofuran (DMSO-THF) as the solvent. [Pg.181]

Propanol, titanium (4+) salt, 65, 230 2-Propanone, l-bromo-3-chloro-, dimethyl acetal, 65, 32 Propargyl bromide (106-96-7), 66, 77, 79, 86... [Pg.130]


See other pages where Dimethyl propargyl is mentioned: [Pg.742]    [Pg.742]    [Pg.247]    [Pg.61]    [Pg.216]    [Pg.777]    [Pg.1057]    [Pg.461]    [Pg.131]    [Pg.854]    [Pg.131]    [Pg.461]    [Pg.291]    [Pg.56]    [Pg.742]    [Pg.742]    [Pg.247]    [Pg.61]    [Pg.216]    [Pg.777]    [Pg.1057]    [Pg.461]    [Pg.131]    [Pg.854]    [Pg.131]    [Pg.461]    [Pg.291]    [Pg.56]    [Pg.107]    [Pg.230]    [Pg.237]    [Pg.148]    [Pg.691]    [Pg.201]    [Pg.519]    [Pg.873]    [Pg.693]    [Pg.870]    [Pg.55]    [Pg.58]    [Pg.497]    [Pg.1048]    [Pg.1084]    [Pg.85]    [Pg.261]    [Pg.499]    [Pg.231]   
See also in sourсe #XX -- [ Pg.163 , Pg.167 , Pg.467 ]




SEARCH



© 2024 chempedia.info