Exclusive Synthesis of β‐Alkylpyrroles under Indium Catalysis: Carbonyl Compounds as Sources of Alkyl Groups

Abstract

Musterbildung mit Proteinen: Ein Protein, das mit einer Azidmarkierung selektiv gekennzeichnet war, wurde mit alkinfunktionalisierter DNA umgesetzt. Die Protein‐DNA‐Konjugate wurden genutzt, um eine mit DNA (blau) aggregierte Proteinnanostruktur (weiß) herzustellen. Die Methode könnte die Erzeugung von Protein‐DNA‐Hybridstrukturen mit nützlichen strukturellen und funktionellen Eigenschaften vereinfachen.

Metal‐Free Regioselective β‐Alkylation of Pyrroles with Carbonyl Compounds and Hydrosilanes: Use of a Brønsted Acid as a Catalyst

“…However, the alkyl unit installable onto 2 was restricted to the secondary alkyl group with a methyl substituent since 1 has been limited mainly to terminal alkynes. We therefore improved the issue by replacing 1 with carbonyl compounds 5 , which serve as a source of a broad range of alkyl groups including primary, secondary and tertiary as well as cyclic structures 8. In addition to the improvement, we envisaged that exploiting a new catalyst in lieu of the indium salt, which includes a rather expensive indium metal9 and is required to be pre‐synthesized,10, 11 would further enhance the practicality and utility of the strategy.…”

Selective Synthesis of β‐Alkylpyrroles

“…We therefore envisioned that replacing 38 with carbonyl compounds 47 would drastically extend the diversity of alkyl groups installable onto 39, giving 48 (Scheme 24). [53] Moreover, it was expected that the use of 47, which is cheaper in general than 38, would make the process highly attractive and practical.…”

“…Under indium catalysis, the strategy can be performed readily by a simple mixing of N-substituted pyrroles 39, Et 3 SiH and either alkynes 38 [52] or carbonyl compounds (see below). [53] The alkyne-based reaction, which has been developed prior to the reaction of carbonyl compounds, is the first example of catalytic b-alkylation of pyrroles in a single step. At first, we present the details of the alkynebased reaction.…”

“…Despite that a,b'-dipyrrolylalkanes 51, which possibly lead to a-alkylpyrroles 55 by the elimination of the b-pyrrolyl ring, exist in the reaction mixture before the trapping with nucleophiles, [52][53][54][55][56] a natural question is why no 55 is formed in this strategy. On the basis of experimental results, we can provide the most plausible interpretation for the question.…”

Indium-Catalyzed Annulation of o-Acylanilines with Alkoxyheteroarenes: Synthesis of Heteroaryl[b]quinolines and Subsequent Transformation to Cryptolepine Derivatives

“…On the other hand, we have recently reported a new C(heteroaryl)–N bond-forming reaction by reacting electron-rich methoxyheteroarenes with amines via a nucleophilic aromatic substitution (S N Ar) reaction [ 54 ]. In addition to this, we have also developed several new C(heteroaryl)–C bond-forming reactions by reacting alkynes [ 55 , 56 , 57 ] or carbonyl compounds [ 58 , 59 , 60 ] with heteroarenes. All of these reactions are effectively catalyzed by a salt of an indium(III) Lewis acid, which has been also employed for various organic transformations by other research groups [ 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 ].…”