7.7- Dimethylallyl bromide

Dimethylallyl bromide 2-Butene, l-bromo-3-methyl- (8,9) (870-63-3) Sodium hydride (8,9) (7646-69-7)... 

Higher yields of 3-substituted products were observed in DoM reactions of2,4-dimethoxy, 2,4,6-trimethoxy, and 2,4,8-trimethoxy quinolines. Furthermore, rt-BuLi metalation of 2,4-dimethoxy, 2,4,6- 2,4,7- 2,4,8-trimethoxy, and 2,4,6,7-tetramethoxy quinolines 337 followed by N-methylformanilide [74T4153 79IJC(B) 115] or 3,3-dimethylallyl bromide [73JCS(P1 )94] quench furnished good to excellent yields of the expected 3-substituted products 338 (Scheme 103). 

A synthesis of lapachol using reaction conditions better than those used by Fieser was carried out by Fridman et al [149].They used the lithium salt of 2-hydroxy-1,4-naphthoquinone prepared in situ instead of the silver salt used for Fieser [150]. The lithium salt was prepared in situ by addition of lithium hydride to the frozen solution of the quinone in dimethyl sulfoxide, Fig. (14). As the solution thawed, the lithium quinone was slowly formed and was then alkylated with 3,3-dimethylallyl bromide. Lapachol was thus obtained in 40% yield. 

Because of the low reactivity of the tertiary alcohol, alkylation of the 014-hydroxyl with alkyl halides such as propyl or isoamyl halides was unsuccessful [Schmidhammer H, unpublished observations]. Therefore, allylic halides were employed to introduce 14-O-alkenyl substituents using similar conditions as described above [ 43—461. Catalytic hydrogenation afforded the corresponding 14-O-alkyl derivatives [43 -5]. Thus, 14-hydroxy-5-methylcodeinone (20) was treated with 3,3-dimethylallyl bromide in DMF in the presence of NaH to give compound 21, which underwent catalytic hydrogenation to yield 14-O-isoamyl-substituted morphinan 24 (Scheme 5) [43]. Similarly 14-phenylpropoxymorphinans 25 and 26 were prepared from 14-hydroxycodeinone (3) and 21, respectively, via intermediates 22 and 23, which were obtained by alkenylation using cinnamyl bromide (Scheme 5) [44, 45],... 

Furoquinoline alkaloids specifically labeled with 14C in the furan ring were required for biosynthetic studies (see Section VII of this chapter), and since existing routes produced low yields, Grundon and co-workers (195, 196) developed a more efficient synthesis from 4-methoxy-3-prenyl-2-quinolones 244-246. These compounds had previously been prepared from aromatic amines and substituted malonates, but direct allylation is more suitable for the preparation of labeled compounds, employing, for example, [14C]-3,3-dimethylallyl bromide. It was found that reaction of... 

Dimethoxyquinoline in tetrahydrofuran treated under Ng with n-butyllithium in hexane, then 3,3-dimethylallyl bromide in tetrahydrofuran added dropwise, and water added after 1 hr. -> 2,4-dimethoxy-3-(3-methylbut-2-enyl)quinoline. Y 81%. F.e. s. J.F. Collins et al., Soc. Perkin I 1973, 94. 

Note Here comes the important point during bromination in the acidic medium, the intermediary allylic carbocation formed on the tert-C atom is in equilibrium with the more reactive pnm-carbocation, which is brominated. This synthesis of 3,3-dimethylallyl bromide TM 2.13a is the basis of multi-ton industrial production since this compound is used in the agrochemical, pharmaceutical and dyestuff fields. 

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