A General Synthetic Route to Isomeric Pyrrolo[1,2- x][1,4]diazepinones

Synthesis of tetrahydrofuro[3,2-c]pyridines via Pictet-Spengler reaction

A semi-one-pot method for the synthesis of 4-substituted tetrahydrofuro[3,2-c]pyridines by the Pictet-Spengler reaction was developed. The method is based on the condensation of easily accessibly 2-(5-methylfuran-2-yl)ethanamine with commercially available aromatic aldehydes followed by acid-catalyzed Pictet-Spengler cyclization. Using this approach, we synthesized a range of 4-substituted tetrahydrofuro[3,2-c]pyridines in reasonable yields. The reactivity of some of the products was investigated and selected synthetic transformations of the obtained tetrahydrofuro[3,2-c]pyridines were shown.

One-Step Synthesis of Triphenylphosphonium Salts from (Het)arylmethyl Alcohols

Two approaches for the synthesis of substituted phosphonium salts from easily available benzyl alcohols and their heterocyclic analogs have been developed. The developed protocols are complementary: the direct mixing of alcohol, trimethylsilyl bromide, and triphenylphosphine in 1,4-dioxane followed by heating at 80 °C was found to be more efficient for acid-sensitive substrates, such as salicyl or furfuryl alcohols as well as secondary benzyl alcohols, while a one-pot procedure including sequential addition of trimethylsilyl bromide and triphenylphosphine gave higher yields for benzyl alcohols bearing electroneutral or electron-withdrawing substituents.

Transformation of 3-(Furan-2-yl)-1,3-di(het)arylpropan-1-ones to Prop-2-en-1-ones via Oxidative Furan Dearomatization/2-Ene-1,4,7-triones Cyclization

The approach to 3-(furan-2-yl)-1,3-di(het)arylprop-2-en-1-ones based on the oxidative dearomatization of 3-(furan-2-yl)-1,3-di(het)arylpropan-1-ones followed by an unusual cyclization of the formed di(het)aryl-substituted 2-ene-1,4,7-triones has been developed. The cyclization step is related to the Paal-Knorr synthesis, but the furan ring formation is accompanied in this case by a formal shift of the double bond through the formation of a fully conjugated 4,7-hydroxy-2,4,6-trien-1-one system or its surrogate.

Modular and Stereoselective Approach to Highly Substituted Indole/Pyrrole-Fused Diazepanones

A one-pot synthetic method for indole/pyrrole-fused 1,4-diazepanone scaffolds has been developed. This method involves a sequential amide coupling/intramolecular aza-Michael addition of 1H-indole/pyrrole-2-carboxylic acids with Morita-Baylis-Hillman-derived allylamines. The readily available starting materials, good stereoselectivity, and gram-scale synthesis make this method valuable for the construction of highly substituted fused heterocycles containing the 1,4-diazepanone moiety.

Intramolecular azavinyl carbene-triggered rearrangement of furans

An intramolecular rhodium-catalyzed reaction of 1-tosyl-1,2,3-triazoles with furans has been explored. The tosylimino functionality was found to play a significant chemical role participating in the subsequent domino-transformations of a key reaction intermediate. One of the reaction pathways leads to valuable 2-formyl- and 2-acetylpyridine building blocks, which could be obtained in one-pot starting from easily accessible (furan-2-ylmethyl)propargyl amines. An original method for the synthesis of highly functionalized indolizines from the obtained pyridines has been proposed.

A Route to (Het)arene-Annulated Pyrrolo[1,2-d][1,4]diazepines via the Expanded Intramolecular Paal-Knorr Reaction: Nitro Group and Furan Ring as Equivalents of Amino Group and 1,4-Diketone

A straightforward protocol toward pharmacologically relevant (het)areno[x,y-b]pyrrolo[1,2-d][1,4]diazepines in good to high yields has been described. The designed approach consists of an acid-promoted furan ring opening in easily accessible N-(2-furylethyl)-2-nitroanilines or their heterocyclic analogues followed by the reductive cyclization of the corresponding nitro-1,4-diketones.