Pictet-Spengler Type Reaction Research Articles

Metal Free Simple and Efficient Synthesis of Tetrahydropyrrolo[1,2-a]- Pyrazine Based on a Cascade Strategy

Abstract: A simple and efficient synthesis of pyrrolo[1,2-a]pyrazine using Schiff base formation, intramolecular cyclization (or N-alkylation), and Pictet–Spengler type reaction (hetero-aromatisation) has been developed. In this chemistry, metal-free, cost and time-effective processes have been highlighted to afford the complex nitrogenous scaffold using simple starting materials.

Organocatalytic Cascade Reactions for the Diversification of Thiopyrano-Piperidone Fused Rings Utilizing Trienamine Activation.

An aminocatalytic privileged diversity-oriented synthesis (ApDOS) strategy utilizing trienamine catalysis for the construction of diverse and complex thiopyrans-piperidone fused rings through a thia-Diels-Alder/nucleophilic ring-closing sequence by using dithioamides as activated heterodienophiles is reported. Following this strategy, a super cascade reaction to assemble nine fused rings can be achieved by employing a bis-dithioamide. Additionally, by linking an indole moiety on the dithioamide, a Pictet-Spengler type reaction can be promoted once the cascade sequence has been achieved, leading to more complex penta- hexa- and heptacyclic fused ring derivatives in a one-pot process. This investigation opens new perspectives for the synthesis of a new class of complex and diverse thiopyrans that contribute to populate new relevant regions in the chemical space.

Synthesis of Isochroman Derivatives via Oxa-Pictet–Spengler Reaction of Vinylogous Esters

Trimethylsilyl triflate (TMSOTf) can be efficiently used for the synthesis of isochromans via Pictet–Spengler type reaction of vinylogous esters in good yields. The methodology is applied for the formal synthesis of key intermediate alcohols for the synthesis of D 4 antagonist sonepiprazole (±)-U-101387 and the isochroman (±)-U-54537.

Facile Synthesis of 1-Aryl-2,3-dihydro-1H-isoindoles by Cyclization of N-Formyliminium Ion via Geometrically Disfavored 5-Endo-trig Process

Synthesis of 1-aryl-2,3-dihydro-1H-isoindoles (isoindolines) (10) was achieved in a highly effective manner via acid catalyzed cyclization of N-formyliminium ion (8) obtained from 2,3-dimethoxybenzylamine and carbonyl compounds with acetic-formic anhydride under a one pot procedure. This Pictet-Spengler type reaction provides a convenient method for preparing 1-arylisoindolines.

Synthesis of Calycotomine via Pictet-Spengler Type Reaction of N,O-Acetal TMS Ethers as N-Acyliminium Ion Equivalents

An efficient Pictet-Spengler type reaction of N,O-acetal TMS ethers for the practical synthesis of 1-substituted tetrahydroquinolines, medicinally important alkaloids, has been accomplished. To demonstrate the versatility of this novel procedure, the total synthesis of calycotomine, a representative 1-hydroxymethyl substituted tetrahydroisoquinoline, is also described.

The Structure of Rauvolfia serpentina Strictosidine Synthase Is a Novel Six-Bladed β-Propeller Fold in Plant Proteins

The enzyme strictosidine synthase (STR1) from the Indian medicinal plant Rauvolfia serpentina is of primary importance for the biosynthetic pathway of the indole alkaloid ajmaline. Moreover, STR1 initiates all biosynthetic pathways leading to the entire monoterpenoid indole alkaloid family representing an enormous structural variety of approximately 2000 compounds in higher plants. The crystal structures of STR1 in complex with its natural substrates tryptamine and secologanin provide structural understanding of the observed substrate preference and identify residues lining the active site surface that contact the substrates. STR1 catalyzes a Pictet-Spengler-type reaction and represents a novel six-bladed beta-propeller fold in plant proteins. Structure-based sequence alignment revealed a common repetitive sequence motif (three hydrophobic residues are followed by a small residue and a hydrophilic residue), indicating a possible evolutionary relationship between STR1 and several sequence-unrelated six-bladed beta-propeller structures. Structural analysis and site-directed mutagenesis experiments demonstrate the essential role of Glu-309 in catalysis. The data will aid in deciphering the details of the reaction mechanism of STR1 as well as other members of this enzyme family.

Nucleophilic Addition to 1,2‐Dimethyl‐3‐arylsulfonyl‐4,5‐dihydroimidazolium Iodides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

NUCLEOPHILIC ADDITION TO 1,2-DIMETHYL-3-ARYLSULFONYL- 4,5-DIHYDROIMIDAZOLIUM IODIDES

ABSTRACT Benzenesulfonamide derivatives 6–11 were prepared from the reactions of arylsulfonylimidazolium iodides 1–5 with malononitrile or nitromethane anions in high yield. The addition product 11 reacted further with tryptamine to produce 2,3,4,9-tetrahydro-1-methyl-1-nitromethyl-1H-pyrido[3,4]indole (12) in excellent yield through Pictet–Spengler type reaction.

2,5-Dimethoxy-2,5-Dihydrofuran as a Synthetic Equivalent of 3-Formyl Alkylpropionate in Pictet-Spengler Type Reactions

2,5-dimethoxy-2,5-dihydrofuran has been used as a synthetic equivalent of 3-formyl propionate in the Pictet-Spengler type reaction of 2-aryl ethylamines to provide the corresponding arylindolizidinones in moderate yields.

A Modified Mannich Reaction Using 1.3-Dioxolane.

Mannich reaction of ketones using 1, 3-dioxolane instead of formaldehyde, paraformaldehyde, or 1, 3, 5-trioxane afforded the corresponding Mannich bases in high yields. Under the same conditions the aminomethylation of aromatics did not proceed but the intramolecular aminomethylation, like a Pictet-Spengler type reaction, proceeded smoothly.

Diastereoselective pictet-spengler reactions of L-(boc)prolinal: a biomimetic synthesis of eudistomins H and I, and woodinine

The carbon skeleton present in eudistomins H, I and in woodinine may be envisioned to be biosynthetically derived from tryptamine and L-prolinal by a Pictet-Spengler type reaction. The diastereoselectivity (5:1) of this reaction, and the elaboration of the Pictet-Spengler products into the title compounds is described. The absolute stereochemistry of (−) woodinine is thereby established.

Studies on the syntheses of heterocyclic compounds. Part DII. Synthesis of 1-substituted 1,2,3,4-tetrahydrophthalazines by a pictet–spengler-type reaction of 3-hydroxybenzylhydrazine with carbonyl compounds

Condensations of 3-hydroxybenzylhydrazine with acetone, ethyl methyl ketone, diethyl ketone, cyclohexanone, and 1-methyl-4-piperidone in the presence of acid gave the 1,1-disubstituted 1,2,3,4-tetrahydrophthalazines (2)–(6). On the other hand, the reactions of 3-hydroxybenzoylhydrazine (7) with acetone, cyclohexanone, and benzalde-hyde gave the Schiff's bases (8)–(10).