3620-81-3

Upstream product

• 90006-46-5 2-chloro-3-ethyl-4-methylpyridine 
• 74300-06-4 3-(3-ethyl-4-methyl-2-pyridyl)indole 
• 130291-34-8 (1RS,5RS,12SR)-12-ethyl-1,2,3,4,5,6-hexahydro-1,5-methanoazocino<4,3-b>indole 
• 48210-16-8 2-(1-benzyl-3-ethyl-piperidin-4-ylmethyl)-indole 
• 128350-31-2 2-(1-Benzyl-2-cyano-3-ethyl-piperidin-4-ylmethyl)-indole-1-carboxylic acid tert-butyl ester 
• 139758-45-5 C₂₄H₂₆N₂O₂ 
• 128350-30-1 C₂₃H₂₆N₂ 
• 28199-32-8 methyl 3-ethyl-2-(3-indolyl)-4-pyridinecarboxylate 
• 189240-59-3 1-(benzenesulfonyl)-3-(3-ethyl-4-methyl-2-pyridyl)indole 
• 159021-44-0 methyl 2-chloro-3-ethylpyridine-4-carboxylate 
• 139750-89-3 (1RS,5RS,12SR)-benzyl 12-ethyl-6-oxo-1,2,3,4,5,6-hexahydro-1,5-methanoazocino[4,3-b]indole-carboxylate 

Relevant academic research and scientific papers

Palladium(0)-catalyzed heteroarylation of 2- and 3-indolylzinc derivatives. An efficient general method for the preparation of (2-pyridyl)indoles and their application to indole alkaloid synthesis

Palladium(0)-catalyzed coupling of (1-(benzenesulfonyl)-2-indolyl)zinc chloride (1) and (1-(tert-butyldimethylsilyl)-3-indolyl)zinc chloride (6) with diversely substituted (alkyl, methoxy, methoxycarbonyl, nitro, hydroxy) 2-halopyridines gives the corresponding 2- and 3-(2-pyridyl)indoles [4 and 7 (or 8), respectively] in excellent yields. A series of other 3-(heteroaryl)indoles (pyrazinyl, furyl, thienyl, indolyl) have been similarly prepared from 6. The potential of some of these (2-pyridyl)indoles in alkaloid synthesis is demonstrated. Thus, from 2-(2-pyridyl)indole 4b, a new synthetic entry to the indolo[2,3-a]quinolizidine system, involving stereoselective hydrogenation of the pyridine ring with subsequent electrophilic cyclization upon the indole 3-position from an appropriately N(b)-substituted 2-(2-piperidyl)indole, is reported. For this purpose, Pummerer cyclizations have been extensively studied. Whereas the indole-unprotected sulfoxide 17 gives the corresponding indoloquinolizidine 19 in low yield and mainly undergoes an abnormal Pummerer cyclization that ultimately leads to sulfide 18, the N(a)-protected sulfoxides 24a and 24b afford the respective indoloquinolizidines 25a,b in 70% yield. On the other hand, the conversion of 3-(2-pyridyl)indole 8k into tetracyclic ketone 35 by stereoselective hydrogenation, followed by cyclization of the resulting all-cis-3-(2-piperidyl)indole 34, represents a formal synthesis of Strychnos alkaloids with the strychnan skeletal type (tubifoline, tubifolidine, 19,20-dihydroakuammicine). A similar conversion of 8j into nordasycarpidone constitutes a formal synthesis of the alkaloids of the uleine group. Reduction of nordasycarpidone leads to tetracycle 37, an advanced intermediate in a previous synthesis of tubotaiwine, a Strychnos alkaloid with the aspidospermatan skeletal type. Finally, piperidylindole 34 was transformed into tetracycle 41, an ABDE substructure of akuammiline alkaloids, by a sequence involving the skeletal rearrangement of an intermediate spiroindolenine as the crucial step.

Short formal syntheses of indole alkaloids of the uleine and Strychnos groups

The formal synthesis of ulcine-type (dasycarpidone, dasycarpidol, uleine, and 17-hydroxy-16,17-dihydrouleine) and Strychnos alkaloids belonging to both the Strychnan (tubifoline, tubifolidine, and 19,20-dihydroakuammicine) and Aspidospermatan (tubotaiwine) skeletal types from 3-(2-pyridyl)indoles is described.