3- bromo isoquinoline

Carbonylation of halides in the presence of primary and secondary amines at I atm affords amides[351j. The intramolecular carbonylation of an aryl bromide which has amino group affords a lactam and has been used for the synthesis of the isoquinoline alkaloid 498(352], The naturally occurring seven-membered lactam 499 (tomaymycin, neothramycin) is prepared by this method(353]. The a-methylene-d-lactam 500 is formed by the intramolecular carbonylation of 2-bromo-3-alkylamino-l-propene(354]. 

True electrophilic substitution is very difficult in pyridopyridazines. For example, the [3,4-d] parent (286) is inert to hot 65% oleum (68AJC1291), and although formation of a 3-bromo derivative (308) was reported in the [2,3-d] series, it seems to have arisen by an addition-elimination reaction via the dibromide (309) (69AJC1745). Attempted chlorination led to ring opening. A similar effect was observed in the [3,4-d] system, where an 8-bromo derivative was obtained (77BSF665), and in iV-oxides of the pyrido[2,3-c]pyridazine and fused pyridazino[3,4-c]isoquinoline series (72JHC351). The formation of (311) from (310)... 

The reactivities of the 1-bromo- and 3-bromo-2-nitronaphthalenes (Table XIII, lines 4, 5, 7 and 8) are markedly different as are those of the isoquinoline analogs discussed below. The uniquely unfavorable... 

Bromoisoquinoline can be aminated under vigorous conditions (concentrated NH4OH, 165°, 16 hr), - but attempted methoxyla-tion (methanolic methoxide, 235°, 7 hr) gave isoquinoline (50% yield) via the reductive reaction observed with 6- and 8-bromo-quinoline. ... 

Isoquinoline 2-oxide was converted by bromine in acetic anhydride in the presence of sodium acetate into the 4-bromo 2-oxide, presumably via an addition-elimination process (84MI2). Metallic derivatives have been used occasionally to prepare bromoisoquinolines, as in the formaton of 79, a process accompanied by ring-opening [87JCS(PI)1865]. 

Isoquinoline must be completely dissolved prior to the addition of N-bromosuccinimide. N-Bromosuccinimide (99%) was purchased from Aldrich Chemical Company, Inc. and recrystallized2 and air-dried prior to use. Recrystallization is essential in order to obtain high yield and pure product. The use of more NBS than stated (i.e., more than 1.1 equiv for the synthesis of 5-bromoisoquinoline and 1.3 equiv for the synthesis of 5-bromo-8-nitroisoquinoline) to obtain complete transformation of isoquinoline should be avoided as this leads to formation of 5,8-dibromoisoquinoline, which cannot easily be separated from 5-bromoisoquinoline and which will also lead to a lower yield of 5-bromo-8-nitroisoquinoline. 

The mechanism of palladium-catalyzed intramolecular cyclization of o-bromo(aminoalkyl)benzenes has been discussed earlier (see Scheme 50 in Section IV,A,4). An example illustrating the use of this approach for the synthesis of 2,3,4,5-tetrahydro-l//-2-benzazepin-l-ones is given in Scheme 17386 and examples indicating the synthesis of isoquinoline derivatives are given earlier (see Scheme 146 in Section V,A,4). 

Vedejs et al. reported catalyst inhibition during a study on the enantioselective transfer hydrogenation of dihydro-isoquinolines using Noyori s catalyst (Scheme 44.2) [27]. Here, the problem is caused by the bidentate nature of the substrate. Whereas the bromo compound 1 a could be rapidly reduced, the tosylamide-sub-stituted compound lb could not be reduced, and although the problem could be alleviated somewhat by alkylation of the sulfmamide to 1 c, hydrogenation of this was still sluggish. Although the authors propose this to be a case of product... 

An interesting palladium-catalyzed allene/azide incorporation and intramolecular 1,3-dipolar cycloaddition cascade to tetrazolo[5,l-tf]isoquinoline has been published by Grigg et al. <2005TL5899>. In the first step of the events, 3-bromo-6-iodobenzonitrile 105 was reacted with the allene/trimethylsilylazide system in the presence of palladium(O) catalyst to yield a coupling product 106 which under the reaction conditions applied (DMF, 70 °C for 24 h) gave 107. 

The Delft synthesis makes use of an acid-catalyzed ring closure - in fact an intramolecular aromatic alkylation - of a l-(3,5-dihydroxy-4-methoxybenzyl) isoquinoline derivative that is prepared starting from (natural) gallic acid. One of the hydroxyl groups is removed via a Pd/ C hydrogenation of the benzyl ether. Other catalytic steps play an important role some steps were improved recently [27]. The crucial step in the Rice synthesis makes use of a l-(2-bromo-5-hydroxy-4-methoxybenzyl)isoquinoline derivative that is also cyclized in an acid-catalyzed ring closure to the morphinan skeleton, followed by catalytic removal of the bromo substituent (Scheme 5.8). 

Amination of 3-bromoisoquinoline with potassium amide/liquid ammonia involves (in contrast to the amination of 2-bromopyridine, see Section an ANRORC process. When 3-bromo[ N]isoquinoline was used as substrate, the 3-aminoisoquinoline being obtained contains 55% of its enrichment on the exocyclic nitrogen, i.e., the formation of 3-[ N-aminoJisoquinoUne (14), and 45% inside the heterocyclic ring, i.e., formation of 3-amino[ N]isoquinoline (13) (74RTC198). 

It has been found that the cupric sulfate-mediated aminolysis of 3-bromo[ N]isoquinoline with ethanolic ammonia (130°C, 7 days reaction time) yields a mixture of 13 and 14, ratio 75 25 (74RTC198). It shows that also with the weaker nucleophile ammonia a part of 3-bromoisoquinoline can undergone a ring-opening, ring-closure process. 

Halogeno-quinolines and -isoquinolines cannot be successfully converted into Grignard reagents but lithium derivatives can be formed from bromo compounds and butyllithium, using low temperatures to prevent addition to the azomethine double bond (Scheme 144) (79JCS(P1)266, 69JHC243). 

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