Stereoselective synthesis of highly substituted 1-isomorphans (1-azabicyclo[3.3.1]nonanes).

We describe the first enantioselective synthesis of highly functionalized 1-azabicyclo[3.3.1]nonanes (1-IM).

The Chameleonic Nature of the Nitro Group Applied to a Base-Promoted Cascade Reaction To Afford Indane-Fused Dihydrofurans.

We disclose a Michael/Conia-ene/S2 cascade reaction for the synthesis of Indane-fused dihydrofurans from 1,3-dicarbonyl compounds and 2-alkynylnitrostyrenes promoted by potassium carbonate in DMSO at room temperature. In this reaction, the nitro group has a chameleonic role, first as an electron-withdrawing group for the Michael addition, then the nitronate behaves as a nucleophile, and finally, the allylic nitro acts as a leaving group. The product is obtained as a single diastereomer, affording up to 82% with 1,3-keto esters and 58% with 1,3-diketones.

Structural Features of Diacyldodecaheterocycles with Pseudo--Symmetry: Promising Stereoinductors for Divergent Synthesis of Chiral Alcohols.

Pseudo--symmetric dodecaheterocyclic structures, which possess two acyl/aroyl groups disposed on either a cis- or trans-relative configuration, were prepared from the naturally occurring (-)-(1)-myrtenal. Addition of Grignard reagents (RMgX) to the diastereoisomeric mixture of these compounds unexpectedly showed that nucleophilic additions to the two prochiral carbonyl centers gave the same stereochemical result in both cis/trans diastereoisomers, making unnecessary the separation of this mixture. Noticeably, both carbonyl groups showed different reactivity because one of them is attached to an acetalic carbon and the other to a thioacetalic carbon.

Incorporation of Conjugated Diynes in Perovskites and their Post-Synthetic Modification.

Two-dimensional (2D) organic-inorganic hybrid perovskites have rapidly become an attractive alternative to three-dimensional (3D) perovskites as solar cell absorbers, owing to their improved stability, versatility, and ease of processing. Despite their advantages, the insulating nature of the organic cations makes these materials have lower absorbing and conducting properties, resulting in lower device efficiencies. A way to circumvent these issues is the integration of functional molecules that help mitigate these limitations.

Stereocontrolled Synthesis of Enantiopure -Fused Octahydroisoindolones via Chiral Oxazoloisoindolone Lactams.

Kinetically controlled cyclocondensation of stereoisomeric and ring-chain tautomeric mixture of (±)-hydroxylactone and 0.5 equiv of ()-phenylglycinol provided tricyclic oxazoloisoindolone lactam (3,5a,9a,9b)-, a versatile intermediate for further stereocontrolled transformations to access enantiopure -fused octahydroisoindolones. An extension of this methodology was successfully applied to the synthesis of the 5,6-dihydroxy derivative (3a,5,6,7a)-.

Water clusters as bifunctional catalysts in organic chemistry: the hydrolysis of oxirane and its methyl derivatives.

This contribution explores the bifunctional catalytic activity of water clusters ((HO) with n = 1-5) in organic chemistry similar to that observed in the formation of HSO in acid rain (Chem. Commun., 53, 3516, (2017)).

The effect of chiral N-substituents with methyl or trifluoromethyl groups on the catalytic performance of mono- and bifunctional thioureas.

We evaluated thiourea organocatalysts that incorporate a chiral group which includes a trifluoromethyl moiety and contrasted their performance with non-fluorinated analogs. The comparison between such systems allows the direct study of the NH acidity of a thiourea bonded to an aliphatic substituent. In principle, -CF3 systems feature an enhanced hydrogen bond (HB) donor capacity that is undoubtedly beneficial for HB-catalysis applied to the Baylis-Hillman reaction.

Stability of doubly and triply H-bonded complexes governed by acidity-basicity relationships.

We used our recently proposed acidity-basicity interplay (ABI) model (Chem. Sci., 2018, 9, 4402) and the Jorgensen secondary interactions hypothesis (JSIH) to rationalise the experimentally observed trends in the formation constants of doubly and triply H-bonded systems with -NHO[double bond, length as m-dash]C- and -NHN- interactions.

Thousand-fold Conductivity Increase in 2D Perovskites by Polydiacetylene Incorporation and Doping.

Two-dimensional (2D) organic-inorganic perovskites have rapidly become an attractive alternative to traditional three-dimensional (3D) perovskite solar-cell absorbers owing to their improved stability and processability. Despite their advantages, the insulating nature of the organic cations and diminished light absorption limit their overall performance. Herein, it is demonstrated that the incorporation of conjugated diynes in hybrid 2D perovskites, and subsequent thermal treatment results in the formation of 2D perovskites that incorporate polydiacetylenes in their structure.

Acidity and basicity interplay in amide and imide self-association.

Amides dimerise more strongly than imides despite their lower acidity. Such an unexpected result has been rationalised in terms of the Jorgensen Secondary Interactions Hypothesis (JSIH) that involves the spectator (C[double bond, length as m-dash]O) and H-bonded (C[double bond, length as m-dash]O) carbonyl groups in imides. Notwithstanding the considerable body of experimental and theoretical evidence supporting the JSIH, there are some computational studies which suggest that there might be other relevant intermolecular interactions than those considered in this model.

Identification of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamate-nitrostyrene hybrid as potent antiproliferative and apoptotic inducing agent against cervical cancer cell lines.

The present study seeks to describe the design and synthesis of six new Michael adducts of (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamate with nitrostyrenes and their in vitro antiproliferative activity against human cervical cancer cell lines [HeLa (HPV 18 positive), CaSki (HPV 16 positive) and ViBo (HPV negative) cervical cancer cell lines].

Stereodivergent Mannich reaction of bis(trimethylsilyl)ketene acetals with N-tert-butanesulfinyl imines by Lewis acid or Lewis base activation, a one-pot protocol to obtain chiral β-amino acids.

We report a one-pot synthesis of chiral β-amino acids by the Mannich addition of bistrimethylsilyl ketene acetals to N-tert-butanesulfinyl imines followed by the removal of the chiral auxiliary. The synthesis and isolation of pure β-amino acid hydrochlorides were conducted under mild conditions, without strong bases and this method is operationally simple. The stereoselective reaction was promoted by two different activation methods that lead to different stereoisomers: (1) Lewis Acid (LA) catalysis with boron trifluoride diethyl etherate and (2) Lewis Base (LB) catalysis with tetrabutylammonium difluorotriphenylsilicate.

Hydrogen-Bond Weakening through π Systems: Resonance-Impaired Hydrogen Bonds (RIHB).

Redefining interactions: The concept of the resonance-impaired hydrogen bond (RIHB) as an interaction in which a conjugated π system strongly impairs the formation of a hydrogen bond (HB) is introduced. A typical HB involving charged species can have a formation energy of tens of kcal mol , whereas the corresponding value for the examined RIHB is only 2.6 kcal mol .

Stereocontrolled Nucleophilic Addition to Five-Membered Oxocarbenium Ions Directed by the Protecting Groups. Application to the Total Synthesis of (+)-Varitriol and of Two Diastereoisomers Thereof.

A stereodivergent C-glycosidation of carbohydrate-derived lactones can be mediated by the protecting groups and applied to the total synthesis of (+)-varitriol and of two diastereoisomers thereof, which represent an unprecedent use of the protecting groups in the synthesis of a naturally occurring compound. In particular, the stereoselective nucleophile attack for 2,3-trans-substituted five-membered ring oxocarbenium ions is strongly influenced by the presence of aromatic rings in the protecting groups. According to quantum chemical calculations, the stereoselectvity depends on the π-π interactions between the aromatic ring of the C-2 protecting group with the exocyclic triple bond and the oxocarbenium ion.

The bifunctional catalytic role of water clusters in the formation of acid rain.

State-of-the-art chemical bonding analyses show that water clusters have a bifunctional catalytic role in the formation of HSO in acid rain. The embedded HO monomers mitigate the change in the chemical bonding scenario of the rate-limiting step, reducing thereby the corresponding activation energy in accordance with Hammond's postulate. We expect that the insights given herein will prove useful in the elucidation of the catalytic mechanisms of water in inorganic and organic aqueous chemistry.

Bifunctional Thioureas with α-Trifluoromethyl or Methyl Groups: Comparison of Catalytic Performance in Michael Additions.

Thioureas are an important scaffold in organocatalysis because of their ability to form hydrogen bonds that activate substrates and fix them in a defined position, which allows a given reaction to occur. Structures that enhance the acidity of the thiourea are usually used to increase the hydrogen-bonding properties, such as 3,5-bis(trifluoromethyl)phenyl and boronate ureas. Herein, we report the synthesis of bifunctional thioureas with a chiral moiety that include either a trifluoromethyl or methyl group.

Mapping the landscape of potentially primordial informational oligomers: (3'→2')-D-phosphoglyceric acid linked acyclic oligonucleotides tagged with 2,4-disubstituted 5-aminopyrimidines as recognition elements.

The (3'→2')-phosphodiester glyceric acid backbone containing an acyclic oligomer tagged with 2,4-disubstituted pyrimidines as alternative recognition elements have been synthesized. Strong cross-pairing of a 2,4-dioxo-5-aminopyrimidine hexamer, rivaling locked nucleic acid (LNA) and peptide nucleic acid (PNA), with complementary adenine-containing DNA and RNA sequences was observed. The corresponding 2,4-diamino- and 2-amino-4-oxo-5-aminopyrimidine-tagged oligomers were synthesized, but difficulties in deprotection, purification, and isolation thwarted further investigations.