DIBAL-H-mediated N-deacetylation of tertiary amides: synthesis of synthetically valuable secondary amines

A rapid DIBAL-H-mediated N-deacetylation of tertiary amides is described under mild conditions, affording synthetically valuable secondary amines in good to excellent yields.

Early Champions of Research in Chemistry with Undergraduates: From William Albert Noyes to Percy Lavon Julian

Research in chemistry with undergraduates is commonplace today, including in many liberal arts colleges. This educational opportunity for undergraduates goes back to the late 1800s, exemplified by William Albert Noyes at Rose Polytechnic, and was honed to an almost graduate-level experience by Percy Lavon Julian at DePauw University in the early 1930s. The connection between Noyes and Julian is discussed in this report. The article traces the origins of scholarly research performed by undergraduate students by Noyes at an institution that is now called the Rose-Hulman Institute of Technology. This model was then replicated and substantially expanded at DePauw University by Noyes's former colleague, William Martin Blanchard. Through sheer happenstance and a series of unfortunate incidents, Julian found himself entrusted with the task of running the undergraduate chemistry research program at DePauw in 1932. Julian's exceptional ability to mentor undergraduate students and to accomplish significant advances in synthetic organic chemical methodologies was highly successful despite the challenging circumstances of racial division, limited financial resources at DePauw during the Great Depression, and job uncertainty (as Julian was being paid by "soft money"). These experiences were undoubtedly formative in shaping Julian's career as a prominent scholar, inventor, and entrepreneur, and to his eventual legacy as one of the most inspirational chemical researchers in history. Julian's mentees at DePauw would also go on to have notable careers in the chemical sciences and allied scientific and academic disciplines.

Well-Defined Phosphine-Free Manganese(II)-Complex-Catalyzed Synthesis of Quinolines, Pyrroles, and Pyridines

Herein, we report a simple, phosphine-free, and inexpensive catalytic system based on a manganese(II) complex for synthesizing different important N-heterocycles such as quinolines, pyrroles, and pyridines from amino alcohols and ketones. Several control experiments, kinetic studies, and DFT calculations were carried out to support the plausible reaction mechanism. We also detected two potential intermediates in the catalytic cycle using ESI-MS analysis. Based on these studies, a metal-ligand cooperative mechanism was proposed.

Mesoionic N-heterocyclic olefin catalysed reductive functionalization of CO2 for consecutive N-methylation of amines

A mesoionic N-heterocyclic olefin (mNHO) was introduced as a metal-free catalyst for the reductive functionalization of CO2 leading to consecutive double N-methylation of primary amines in the presence of 9-borabicyclo[3.3.1]nonane (9-BBN). A wide range of secondary amines and primary amines were successfully methylated under mild conditions. The catalyst sustained over six successive cycles of N-methylation of secondary amines without compromising its activity, which encouraged us to check its efficacy towards double N-methylation of primary amines. Moreover, this method was utilized for the synthesis of two commercially available drug molecules. A detailed mechanistic cycle was proposed by performing a series of control reactions along with the successful characterisation of active catalytic intermediates either by single-crystal X-ray study or by NMR spectroscopic studies in association with DFT calculations.

Synthesis of Tetrahydroquinolines via Borrowing Hydrogen Methodology Using a Manganese PN3 Pincer Catalyst

A straightforward and selective synthesis of 1,2,3,4-tetrahydroquinolines starting from 2-aminobenzyl alcohols and simple secondary alcohols is reported. This one-pot cascade reaction is based on the borrowing hydrogen methodology promoted by a manganese(I) PN³ pincer complex. The reaction selectively leads to 1,2,3,4-tetrahydroquinolines thanks to a targeted choice of base. This strategy provides an atom-efficient pathway with water as the only byproduct. In addition, no further reducing agents are required.

One-Pot, Tandem Wittig Hydrogenation: Formal C(sp3)-C(sp3) Bond Formation with Extensive Scope

A one-pot, tandem Wittig hydrogenation of aldehydes with stabilized ylides is reported, representing a formal C(sp³)-C(sp³) bond construction. The tandem reaction operates under mild conditions, is high yielding, and is broad in scope. Chemoselectivity for olefin reduction is observed, and the methodology is demonstrated in the synthesis of lapatinib analogues and a formal synthesis of (±)-cuspareine. Early insights suggest that the chemoselectivity observed in the reduction step is due to partial poisoning of the catalyst, after step one, thus adding to the power of the one-pot procedure.

Diastereoselective Construction of Cyclopropane-Fused Tetrahydroquinolines via a Sequential [4 + 2]/[2 + 1] Annulation Reaction

A sequential [4 + 2]/[2 + 1] annulation of α-aryl vinylsulfoniums with 2-aminochalcones and 2-(2-aminobenzylidene)-1H-indene-1,3(2H)-dione is reported that affords a series of cyclopropane-fused tetrahydroquinolines. The salient features of this novel and practical transformation include high efficiency, transition-metal-free nature, operational simplicity, and outstanding functional group tolerance.