W-Allylanilines

The application of Heck cyclizations to the synthesis of indoles, indolines, and oxindoles was discovered independently by Mori-Ban s [296-298], and Heck s groups [299]. These investigators found that Pd can effect the cyclization of o-halo-lV-allylanilines to indoles under Heck conditions [300], The cyclization of o-halo-/V-allylanilines to indojes is a general and efficient methodology, especially with the Larock improvements where he cyclized o-halo-W-allylanilines and o-halo-N-acryloylanilides into indoles and oxindoles [301]. For example, the conversion of 279 to 280 can be performed at lower temperature, shorter reaction time, and with less catalyst to give 3-methylindole (280) in 97% yield. Larock s improved conditions, which have been widely adopted, are catalytic (2%) Pd(OAc)2, n-Bu4NCl, DMF, base (usually... 

Diallyl (1) ( 30%) was distilled off and W-allylaniline (4) (45—60%), iV, -diallylaniline (5) (8—10%) and allylalcohol ( 5%) were isolated after deboronation of the residue (Table 1). Negligible amounts of aniline as well as the products of allylation of N-allylaniline in aromatic ring and in a-position of the allylic group were also detected. Trimethallylborane reacts in the same way to produce dimethallyl (33%), A -methallylaniline (57%), A, 7V-dimethallylaniline (8.5%) and negligible co-products. Similar products were isolated fi om the allylboration of / -chloronitrobenzene, and o- and p-nitrobiphenyl (Table 1). 

IV-allylaniline (1.33 g, 10 mmol) was admixed with Zn2+ montmorillonite and subjected to microwave irradiation at 650 W (BPL, BMO-700T, operating at 2450 MHz) for 3 min. After cooling down to room temperature, the reaction mass was directly charged on a silica gel column (100-200 mesh) and eluted with ethyl acetate-rc-hexane (3 7) to afford 2-methylindoline (1.06 g, 80% yield) as pale yellow liquid. 

A general route to allylanilines, reported by Harmata and co-workers <95TL4769> could be of value in organic synthesis. Deprotonation of 2,1-benzothiazines 193 with w-BuLi followed by alkylation with iodomethyltrimethylsilane, and subsequent desilylation with fluoride followed by hydrolysis led to allyl aniline 194 in good yields (Scheme 54). 

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