Synthesis, crystal structure and Hirshfeld surface analysis of tert-butyl N-acetyl-carbamate.

This article reports a practical synthesis of tert-butyl acetyl-carbamate, C7H13NO3, from N-Boc-thio-acetamide and the study of its crystal structure. The reaction proceeds in the presence of natural phosphate as a catalyst, with excellent yield, simple workup and benign environment. The crystal structure was refined using a transferred multipolar atom model. In the crystal, symmetrical pairs of strong N-H⋯O hydrogen bonds connect the mol-ecules into dimers with an R 2 2(8) ring motif. The inter-actions between neighbouring dimers are mostly van der Waals, between hydro-phobic methyl groups. Hirshfeld surface analysis shows the major contributions to the crystal packing are from H⋯H (42.6%) and O⋯H (26.7%) contacts.

Autotandem Catalysis: Inexpensive and Green Access to Functionalized Ketones by Intermolecular Iron-Catalyzed Amidoalkynylation/Hydration Cascade Reaction via N-Acyliminium Ion Chemistry.

Iron-based catalysts were applied in cascade-type reactions for the synthesis of different carbonyl compounds. The reactions proceeded by a new iron-catalyzed cascade of alkynylation/hydration by using both the σ- and π-Lewis acid properties of iron salts. The alkynylation reactions of several endo and exocyclic acetoxylactams were achieved with three different catalysts including FeCl3 ⋅ 6H2 O, FeCl3 , and Fe(OTf)3 showing the efficiency of σ-Lewis acidity of iron (III) salts in catalyzing the alkynylation reaction. We also demonstrated that the reaction sequence could be shortened by the direct use of hydroxylactams, leading to an environmentally friendly protocol, avoiding the need to perform unnecessary lengthy steps. A combination of the hard/soft iron Lewis acid properties was then used to implement an unprecedented tandem intermolecular alkynylation/intramolecular hydration sequence allowing expedient access to a new carbonyl structures from trivial materials.

Highly Enantioselective Semisynthesis of (+)/(-)-Gossypol Schiff Base Derivatives from Ground Plant Material.

We have recently developed a one-pot process for simultaneous extraction and chemical modification (SECheM) on Cienfuegosia digitata, a Mauritanian Malvaceae called locally "Izide". On the basis of this innovative methodology that consisted of using ground plant roots as starting material in gossypol Schiff base semisynthesis, we now report how this concept can be used to access enantiomerically pure Schiff base atropisomer derivatives of gossypol in only two steps. This study has been envisioned since enantiomerically pure Schiff base atropisomer derivatives of gossypol are generally more potent biologically when compared to racemic gossypol Schiff bases.

Development of SECheM Concept for Isolation and Chemical Modification of Gossypol Directly from Cienfuegosia digitata.

INTRODUCTION: Gossypol is an axially chiral natural polyphenol classically extracted from the Malavaceae family. Nevertheless, its extraction and isolation from a plant can be quite complicated and extremely time-consuming since gossypol is known to be sensitive to degradation under solvents, high temperature and light action. Moreover, its purification over column chromatography is a challenging problem due to its ability to oxidise and the existence of various tautomer forms. OBJECTIVE: To develop an efficient "one-step" strategy for simultaneous extraction and semi-synthesis by short-circuiting critical gossypol isolation and purification steps. METHODOLOGY: Gossypol was first isolated from Cienfuegosia digitata roots, characterised (by 1D and 2D NMR) and quantified (by UV spectrophotometry). Thus, aniline was selected to test the "one-step" in situ trapping of freshly extracted gossypol leading to a Schiff base analogue. After screening solvents and extraction times on this model reaction, the "SECheM" (simultaneous extraction and chemical modification) concept was successfully extended to other amines, underlining the efficiency and the robustness of the strategy. RESULTS: After having shown that gossypol occurred as a major compound in C. digitata roots, different experimental procedures using Soxhlet extraction in the presence of aniline pointed out the best conditions for the SECheM concept (7 h of reaction and extraction time in ether as solvent). Ultimately, the concept has been generalised to 17 other amines. CONCLUSION: This is a report of the first semi-synthesis that allows: (1) "in situ" preparation of more stable gossypol Schiff base derivatives directly from ground plant material and (2) circumvention of gossypol extraction and purification problems. Copyright © 2017 John Wiley & Sons, Ltd.