Diastereoselective Ritter-like Reaction on Cyclic Trifluoromethylated N,O-Acetals Derived from l-Tartaric Acid

Trifluoromethylated lactams: promising small molecules in the search for effective drugs

Lactams are a crucial class of compounds with broad therapeutic applications, including in the treatment of cancer, diabetes, and infectious diseases. Functionalised lactams are essential core structures in numerous alkaloids and pharmaceuticals. The introduction of fluorine-containing groups, such as a trifluoromethyl (CF3) group, into organic molecules significantly alters their physical and chemical properties. This review highlights the primary biological targets, as well as the most important synthetic pathways, associated with trifluoromethylated β-lactams (four-atom rings), γ-lactams (five-atom rings), δ-lactams (six-atom rings), and ε-lactams (seven atom rings). Furthermore, we analyze the most common lactam scaffolds, evaluating their potential for future chemical synthesis and emphasizing those that merit attention despite having limited reported analogues. This article aims to provide a comprehensive overview of the importance of trifluoromethylated lactams in drug discovery and design.

C-H bond cleavage-enabled aerobic ring-opening reaction of in situ formed 2-aminobenzofuran-3(2H)-ones

A C-H bond cleavage-enabled aerobic ring-opening reaction of 2-aminobenzofuran-3(2H)-ones formed in situ by hemiacetals with a variety of amines is reported. This simple one-pot reaction provides an alternative approach to obtain o-hydroxyaryl glyoxylamides in excellent yields of up to 97%. Alkylamines react with hemiacetals via a catalyst-free dehydration condensation to generate 2-aminobenzofuran-3(2H)-ones. The in situ formed semicyclic N,O-acetals undergo the same amine-initiated C-H bond hydroxylation in air under mild conditions to afford ring-opening products. Similarly, arylamines were investigated as substrates for a two-step tandem process involving a DPP-catalyzed condensation followed by a Et₂NH-mediated C-H hydroxylation. Unlike the previously reported functionalization of N,O-acetals via a C-O or C-N cleavage, the aerobic oxidative C-H hydroxylation in this reaction, which is promoted by using stoichiometric amounts of alkylamines as both a Lewis base and a reductant at room temperature under atmospheric air, proceeds via α-carbonyl-stabilized carbanion intermediates from the C-H cleavage of N,O-acetals.

TMSOTf-mediated synthesis of skipped dienes through the addition of olefins to imines and semicyclic N,O-acetals

A novel approach to skipped dienes has been developed through the TMSOTf-mediated one-pot addition-substitution of olefins 2a, 2f and 2g with imines 1a-1g, and a series of aryl substituted skipped dienes 3aa-3gf were accordingly obtained in 62%-94% yields. Moreover, semicyclic N,O-acetals 5 and 7 could also undergo this transformation to produce the corresponding skipped dienes 6aa and 6af-6al and 8ba and 8bf-8bk in moderate to good yields.

CF3-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

"The extraordinary instability of such an "ion" accounts for many of the peculiarities of organic reactions" - Franck C. Whitmore (1932). This statement from Whitmore came in a period where carbocations began to be considered as intermediates in reactions. Ninety years later, pointing at the strong knowledge acquired from the contributions of famous organic chemists, carbocations are very well known reaction intermediates. Among them, destabilized carbocations - carbocations substituted with electron-withdrawing groups - are, however, still predestined to be transient species and sometimes considered as exotic ones. Among them, the CF3-substituted carbocations, frequently suggested to be involved in synthetic transformations but rarely considered as affordable intermediates for synthetic purposes, have long been investigated. This review highlights recent and past reports focusing on their study and potential in modern synthetic transformations.

Recent advances of Ritter reaction and its synthetic applications

This review provides a comprehensive survey of Ritter reactions from 2014 to 2020.

cis-Dihydroxylated α-Trifluoromethylated N,O-Acetal from l-Tartaric Acid: Synthesis of Tetrasubstituted Stereocenter via Diastereoselective Pictet-Spengler Cyclization of N-Acyliminium Ions

The synthesis of cyclic, chiral α-trifluoromethylated N,O-acetals having a protected cis-diol moiety has been readily achieved in two steps from a known bis-Weinreb amide derived from l-tartaric acid. The reaction of O-acetyl analogues of these N,O-acetals with triflic acid in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) at 0 °C generated in situ the corresponding electrophilic α-trifluoromethyl N-acyliminium ions that undergo Pictet-Spengler-type cyclizations. After only 10 min of reaction, the original enantiopure aza-tricyclic scaffolds bearing a trifluoromethyl substituent at the bridgehead position were obtained with diastereoselectivities ranging from 75:25 to 97:3.

Chemoselective direct reductive trifluoromethylation of amides: a flexible access to functionalized α-trifluoromethylamines

A one-pot method is reported for the direct transformation of secondary amides to α-trifluoromethylamines.