Dimethylallyl chloride

Hardy effect.248-249 The internal return part of the ionization equilibrium is particularly hard to detect since it is almost completely independent of the concentration of anything in the bulk of the solution outside of the solvent cage. The extent of internal return will depend on the reactivity of the cage walls and their resistance to the escape of either ion. Unless internal return has been eliminated by the use of an extremely reactive cage wall, the measured rate is not that of the ionization but the lesser rate of ion pair dissociation. In the case of the acetolysis of a, a-dimethylallyl chloride (XXXIX), internal return is detectable by virtue of the fact that the chloride ion can return to either of two allylic carbon atoms.248... 

Carbazole can be efficiently tetra-ferf-butylated with tcrt-butylchloride and aluminium chloride at room temperature giving 141 K. 4i,85. traces of 3,6-di- and 1,3,6-tri-tert-butylcarbazoles are also produced. 3-Formyl-2-hydroxycarbazole is alkylated at C-1 with dimethylallyl chloride in the presence of 30% aqueous potassium hydroxide. ... 

Allylic systems have also provided fertile ground for investigation of ion-pair phenomena. Young, Winstein, and Goering established the importance of ion pairs in solvolysis of these compounds. They showed that ion pairs are responsible for the rearrangement of a,a-dimethylallyl chloride to y,y-dimethyl-allyl chloride (Equation 5.8).24 Goering s labeling methods have subsequently supplied a number of details about allylic ion-pair structure.25... 

Isoprene reacts with dimethylallyl chloride in the presence of CuC1-A1203 to yield geranyl chloride, neryl chloride, lavandulyl chloride, and myrcene(12) 111 reaction of (39 X = C1) with antimony trichloride gives (E)- and (Z)-2,6-dimethylocta-2,5,7-trien-4-one.111 (E)- and (Z)-3,7-Dimethylocta-3,6-dien-l-ols, geraniol (8), nerol (18), and the dienol (40) are prepared from isopentenyl acetate and prenyl chloride... 

Further studies on the pyrolysis of chlorinated and brominated hydrocarbons have been reported by Maccoll et al. for 3-bromopentane , menthyl and neo-menthyl chlorides , r-alkyl chlorides , dimethylallyl chlorides , a-chloro-o-xylene , and substituted 1-phenylethyl chlorides . Other workers have reported on the thermal reactions of ethyl chloride , monochloropentanes , 1-... 

Complications may arise where rearrar ement occurs in a step subsequent to nucleophilic substitution. For example Gagneux, Winstein and Young have shown that y,y-dimethylallyl chloride (39) affords a mixture of the azides 40 and 41 on treatment with azide ion (equation 29). The pure azides, separated by g.l.c., rapidly equilibrated to the isomeric mixture. On the basis of the known ability of aryl and alkyl azides to add to olefins, these authors suggested that the isomerization process was conceivably similar in character to an intramolecular addition for which intermediates such as 42 and 43 could be visualized. A possible alternative pathway for this... 

Young et reported in 1951 that the solvolysis of a,a-dimethylallyl chloride in acetic acid buffered with potassium or lithium acetate is accompanied by partial isomerization to 7,7-dimethylallyl chloride, which solvolyzes only about an eighth as fast as its tertiary isomer. It was possible to calculate from the titrirnetric data rate coefficients for the isomerization reaction as well as for the two solvolysis reactions. Since neither the reaction rates nor the product compositions were influenced by added potassium chloride, it was concluded that the isomerization is intramolecular. This is the first documented example of internal return from a carbonium ion-anion pair, viz ... 

The solvolysis and isomerization of a,a-dimethylallyl chloride in aqueous 75% ethanol is more complex In this solvent, the rate of isomerization at 25°C is doubled by the addition of molar LiCl. In the presence of 0.68 M Li Cl, about 63% of the chlorine incorporated into the primary chloride during rearrangement came from radioactive chloride in solution. Thus, under these conditions isomerization involves external return of chloride from solution as well as internal return from a tight ion pair intermediate. a-Phenylallyl chloride also undergoes simultaneous solvolysis and allylic... 

Early evidence for ion pairing was reported by Winstein from the reaction of a,a-dimethylallyl chloride (14) in acetic acid with added acetate. Although the major product of the reaction was the expected acetate, there was rapid isomerization of 14 to the isomeric Y,y-dimethylallyl chloride (15, equation 8.24). Formation of 15 can be explained by a mechanism in which the nucleofuge. Cl , competes as a nucleophile with solvent and rebonds to the allyl cation at the less hindered position. The rate of formation of 15 was found not to be a function of the concentration of added chloride ion, however. This finding is significant because the rate of the solvolysis should be decreased by addition of chloride ion if the mechanism involves dissociation of 14 to free ions (see equation 8.16). It appears, therefore, that the chloride ion in 15 must originate in the same molecule and not from the bulk medium. This process was characterized as internal return of a chloride ion held as part of intimate ion pair (16) within a solvent shell. Similar conclusions were obtained from... 

The reaction between 1 mmol of K[Rh(Pp3)4] and 1 mmol of l-chloro-3-methylbut-2-ene (1,1-dimethylallyl chloride) in diethyl ether gave a yellow solution and a white precipitate. Fractionation of the yellow solution yielded PF3 (ca. 1 mmol) and a yellow volatile liquid A. 

In allylic systems, favorable overlap of the p orbitals of the n system should require a coplanar arrangement of the three sp2 carbons and their five substituent atoms evidence that such a structure is indeed preferred comes, for example, from proton magnetic resonance observations that demonstrate barriers to bond rotation in the isomeric dimethylallyl ions 21, 22, and 23. These ions form stereo-specifically from the three dimethylcyclopropyl chlorides (Section 12.2), and barriers to rotation about the partial double bonds are sufficiently high to prevent interconversion at low temperature. At — 10°C, 21, the least stable isomer,... 

The initial study in this area employed the meso-1,3-dimethylallyl ligand.432 The chloride dimer was generated from 2-pentene, and a variety of optically active phosphine ligands were added to form the chiral bisphosphine complexes. Reaction of these allyl complexes with sodiodiethyl malonate resulted in optical yields in the range of 2-29% (equation 351). 

Compounds of type LXXIII cannot be made by the rearrangement of the 7-substituted allyl ethers, because these compounds yield LXXIV by inversion. a,7-Dimethylallyl bromide,16 7,7-dimethylallyl bromide,29 cinnamyl chloride,84 and phytyl bromide 86 (a vitamin K synthesis) have been used in C-alkylation procedures. The silver salt of 2-hydroxy-l,4-naphthoquinone is converted to a mixture of C-alkylation product and two isomeric ethers by treatment with allylic halides and benzyl halides. ... 

Terpenoid Synthesis from Isoprene.—Interest continues in new syntheses of iso-prene and its derivatives the dioxan (37) is obtained108 in good yield by the Prins reaction of methylallyl chloride with formaldehyde (cf. Vol. 5, p. 8) free-radical addition of isopropyl alcohol to vinyl acetate yields compound (38) which gives isoprene by acid-catalysed reaction over alumina.109 (Z)-2-Methylbut-2-en-l-ol and dimethylallyl alcohol are readily available from frans-crotyl alcohol.110... 

Chloro-3-methyl-l-butene Chloride ion 1,1-Dimethylallyl cation... 

Dimethylallyl alcohol y.y-Dimethylallyl alcohol. See 3-Methyl-2-buten-1-ol Dimethylaluminum chloride CAS 1184-58-3 EINECS/ELINCS 214-668-8 Synonyms Aluminum, chlorodimethyl- DMAC Classification Metal alkyl organometallic compd. Empirical C2H6AICI Formula (CH3)2AICI... 

Preparative Methods treatment of trichlorosilane with 3-methylbut-2-en-l-ylmagnesium chloride followed by methylmagnesium bromide (2 equiv) provides (aja-dimethyl-allyl)dimethylsilane (bp 108 °C) in 76% yield with 99% isomeric purity. The hydrosilane is converted to the ethoxysi-lane quantitatively by the reaction with ethanol catalyzed by hydrogen hexachloroplatinate(IV), and then fluorinated in situ with tetrafluoroboric acid to give the fluorosilane in 87% yield. The latter is methylated with a small excess of methyllithium to give (Q, Q -dimethylallyl)trimethylsilane in 96% yield. Alternatively, (a,Q -dimethylallyl)trimethylsilane can be prepared from 3-methylbut-l-yn-3-ol in six steps. ... 

Prenylation of Acetals. (a,a-Dimethylallyl)trimethylsilane reacts with acetals in the presence of a Lewis acid to give the corresponding homoallyl alcohols with corr5)lete regioselectivity (eqs 1 and 2). The reaction with carbonyl compounds often leads to the formation of tetrahydrofuran derivatives (eq 3), presumably through the formation of chloride. ... 

Indole added to a soln. of succinimido-(3,3-dimethylallyl)(ethyl)sulfonium chloride prepared at -30° under Ng from 3,3-dimethylallyl ethyl sulfide and N-chlorosuc-cinimide in methylene chloride, and the temp, raised gradually to 35° during 1 hr. 2-(l,l-dimethylallyl)-3-ethylthioindole. Y 58%. F. e. s. K. Tomita, A. Te-rada, and R. Tachikawa, Heterocycles 4, 733 (1976). 

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