Heterocyclics pyrrolo indoles

Condensed and other heterocyclic systems Nitrogen systems. Pyridazine 67 reacted with 10 and aromatic aldehydes to yield phthalazines 68. Arylideneindolinones 69 underwent Michael addition with 10. By subsequent cyclization pyrrolo-indoles 70 were formed Conjugated azoalkenes 71 and 10 gave pyrrolopyrroles 11. ... 

Generally, cycloadditions represent powerful reactions for construction of heterocycles. Tandem intramolecular Diels-Alder/retro-Diels-Alder reaction sequences were applied in the syntheses of many A,B-diheteropentalenes <1996GHEC-II(7)1>. Gribble and co-workers <1998SL1061> reported new syntheses of pyrrolo[3,4-, ]indoles 426, benzo[4,5]furo[2,3-f]pyrroles 429, and benzo[4,5]thieno[2,3-4pyrroles 430 using the 1,3-dipolar cycloaddition... 

The preparation and study of tautomers derived from 2-(2 -pyridyl)indole, 2-(2 -pyrrolo)[l,8]naphthyridine, and related heterocycles has been undertaken using ultraviolet (UV) and nuclear magnetic resonance (NMR) spectroscopy and also by molecular orbital (MO) calculations <1998JOC4055>. 

Padwa and coworkers found that a-cyanoaminosilane 12a is a convenient synthon for azomethine ylide 15 which is extensively used in heterocyclic synthesis [7]. AgP has been adopted to generate the ylide 15 from 12a for the preparation of pyrrolidine derivative 14 (Sch. 4). Various dipolarophiles including A-phenylmaleimide (13) can be used for the cycloaddition. When iV-[(trimethylsilyl)methyl]-substituted indole 16 is reacted with AgP in the presence of maleimide 13, pyrrolo[l,2-a]indole 17 is formed in good yield, retaining the CN group [8]. A silver-bonded carbonium ion is assumed to be a reactive intermediate. Reaction of a cyano-substituted azomethine ylide, derived from (silylmethylamino)malononitrile 12b and AgP, with methyl propiolate (18) provides 3-carbomethoxy-A-benzylpyrrole (19) [9]. Epibatidine, a novel alkaloid, was successfully synthesized by employing the [3 + 2] cycloaddition of azomethine ylide with electron-deficient alkenes as a key step [10]. 

Since CHEC-I appeared in 1984, several reviews on specific fused (5,5,6) heterocycles have been published. A review on pyrrolo[l,2-a]indoles has appeared in which the different synthetic approaches leading to this particular heterocyclic assembly have been systematized <86RTC199>. Special interest of the authors in the five most important strategies leading to the pyrrolo[l,2-ajindole skeleton has been shown, of which the greater part is related to the synthesis of the mitomycins, alkaloid-type antibiotics with antitumor activity. The literature cited covered the period from 1978 to the end of 1985. 

Moreover, a VNS was a key step in the first synthesis of pyrrolo[3,2-e]indole -a heterocyclic fragment of the antitumor antibiotic CC 1065. The a-cyano side chain is installed at the C-4 position on V-(benzyloxymethyl)-5-nitroindole 39 in good yield [25]. This intermediate (40) is then reductively cyclized using Pd(C) to produce the new ring system 41 in 69% yield however, the protecting group does not remain intact at 65°C. If this reaction is carried out at 45°C, the benzyloxy-methyl (BOM) group is left intact, and the pyrrolo[3,2-c]indole is isolated in 62%. 

Gribble GW, Pelkey ET et al (1998) New syntheses of pyrrolo[3,4-b]indoles, benzo[b]furo [2,3-c]pyrroles, and benzo[b]thieno[2,3-c]pyrroles. Utilizing the reaction of muenchnones (l,3-oxazolium-5-olates) with nitro heterocycles. Synlett 1061-1062... 

This reaction has been used to prepare a variety of heterocycles, including 5-aza-indoles 5-,6-, and 7-aza-indoles pyrrolo[3,2-c]quinolines 12-methoxy-A -methyl-vellosimine (-i-)-12-methoxyaffinisine and (-)-fuchsiaefoline. ... 

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