Control of polymorphic transition inducing preferential enrichment

Preferential enrichment is an unusual symmetry-breaking enantiomeric resolution phenomenon that is initiated by the solvent-assisted solid-to-solid transformation of a metastable polymorphic form into a thermodynamically stable one during crystallization from the supersaturated solution of a certain kind of racemic crystals. On the basis of the proposed mechanism of preferential enrichment, both induction and inhibition of preferential enrichment were successfully achieved by controlling the mode of the polymorphic transition during crystallization either by minor molecular modification or with appropriate seed crystals. Furthermore, by inducing a desired polymorphic transition during crystallization of several α-amino acids or their cocrystals with dicarboxylic acids, which were classified as a racemic compound, preferential enrichment could also be accomplished

An expedient synthesis of tetrakis (cyclopropylmethyl) methane

Synthesis of tetrakis(cyclopropylmethyl)methane, a new symmetric product has been described using the radical mediated gem-diallylation of cyclopropylmethyl xanthate as a key step and its single crystal X-ray analysis established its C2-symmetry

Di-tert-butyl N,N′-(octa­hydro­penta­lene-2,5-di­yl)dicarbamate

In the molecule of the title compound, C18H32N2O4, the central bicyclo­[3.3.0]octane (octa­hydro­penta­lene) has a rigid ring junction. Both rings of the bicyclo­[3.3.0]octane unit adopt an envelope conformation, and the flexible tert-butyl­carbamoyl side chains each have an extended conformation. Such a constrained bicyclo­[3.3.0]octane aliphatic template is of inter­est with respect to the design of novel self-assembling motifs. Mol­ecules related by c-glide symmetry are linked via inter­molecular N—H⋯O hydrogen bonds, forming a two-dimensional layer structure. Neighboring layers are weakly associated along the a axis due to the close approach of the tert-butyl­carbamoyl groups (2.55 Å)

Experimental and computational analysis of supramolecular motifs involving C sp2 (aromatic)--F and CF 3 groups in organic solids

info:eu-repo/semantics/publishe

Crystal structure of 1-(4-bromophenyl)but-3-yn-1-one

The title compound, 1-(4-bromophenyl)but-3-yn-1-one, C10H7BrO, crystallizes in the monoclinic space group P21/n with one molecule in the asymmetric unit. The structure displays a planar geometry. The crystal structure is consolidated by C—H...O hydrogen bonding and a short C=O...C[triple-bond]C (acetylene) contacts. Hirshfeld surface analysis indicates that H...H, C...H/H...C and H...Br/Br...H interactions play a more important role in consolidating the crystal structure compared to H...O/O...H and C...C contacts

The influence of electronic factors on palladium-mediated cycloisomerization: A systematic investigation of competitive 5-exo-dig versus 6-endo-dig cyclizations of sugar alkynols

Pd-mediated cycloisomerization of 3-C-alkynyl-allo- and ribofuranose derivatives was investigated in detail to understand the influence of electronic factors on the regioselectivity in ring closure reaction. The reactions in general are influenced by the electronic nature of the substituent on the alkyne unit. A preference for endo-dig cyclization over exo-dig is noted, if the alkynyl substituent is not sufficiently electron withdrawing

Steric control in Pd-mediated cycloisomerization of sugar alkynols: Documentation of a rare allylic epimerization

Pd-mediated cycloisomerization of C3-alkynylated glucofuranosyl derivatives revealed a dominance of steric factors over electronic factors. However, the intermediate glycals were epimerized prior to the ketalization and afforded the more stable cis-fused bicyclic ketals

An expeditious one-step entry to the tetracyclic core of integrastatins

Herein we describe a one-step assembly of structurally complex small molecules representing the central skeleton of integrastatins by employing a simple pinacol transform

Occurrence of spontaneous resolution of ketoprofen with a racemic crystal structure by simple crystallization under nonequilibrium preferential enrichment conditions.

Nearly racemic ketoprofen, which satisfies the requirements for the occurrence of preferential enrichment, was spontaneously resolved into the two enantiomers by simple crystallization under nonequilibrium conditions using high concentrations

A Cu(I)-promoted one-pot ‘S<SUB>N</SUB>Ar–click reaction’ of fluoronitrobenzenes

A one-pot two-step sequence involving a nucleophilic aromatic substitution (S<SUB>N</SUB>Ar) of activated fluorobenzenes with azide nucleophile and in situ Huisgen cycloaddition of the resulting aryl azides with alkynes has been developed for a rapid access to 1,4-substituted triazoles. Control experiments revealed that both the steps are catalyzed by Cu(I) and also the course of reaction as SNAr followed by [3+2]-cycloaddition