Catalytic Asymmetric Synthesis of Allylic Alcohols and Derivatives and their Applications in Organic Synthesis

Allylic alcohols represent an important and highly versatile class of chiral building blocks for organic synthesis. This Review summarizes the plethora of methods developed for the catalytic asymmetric synthesis of enantioenriched allylic alcohols. These include: dynamic kinetic resolution (DKR/DKAT), nucleophilic 1,2‐addition to carbonyl groups, allylic substitution, oxidation of C? H bonds, the addition of O nucleophiles to π systems, reduction of unsaturated carbonyl compounds, and an alternative route from enantioenriched propargylic alcohols. Furthermore, these catalytic asymmetric processes are exemplified by their applications in the syntheses of complex molecules such as natural products and potential therapeutic agents.     

Efficient Synthesis of New Nucleoside Analogues with a Methylenecyclobutane Unit

Synthesis of eight nucleoside analogues 4–11 with a methylenecyclobutane unit is described. Wittig reaction with 2‐hydroxymethylcyclobutanone 12 gave a mixture of Z (13) and E (14) derivatives, which was separated before functional modifications. The heterocyclic moieties were introduced via a Mitsunobu reaction either on the saturated chain or on the unsaturated chain. When adenine was used in this reaction, only the N‐9 substitution products were obtained. Removal of the protecting groups provided the target products.     

Improved Synthesis of 1-Bromo-3-buten-2-one

A convenient procedure for the synthesis of 1-bromo-3-buten-2-one, 4, from commercially available 2-ethyl-2-methyl-1,3-dioxolane, 1, is described. The procedure involves three reaction steps: (1) The acetal 1 is converted to 2-(1-bromoethyl)-2-bromomethyl-1,3-dioxolane, 2, by reacting 1 with elemental bromine in dichloromethane to yield 98% of 2. (2) Dehydrobromination of 2 with potassium tert-butoxide in tetrahydrofuran gives 2-bromomethyl-2-vinyl-1,3-dioxolane, 3, in 84–93% yield. (3) Removal of the acetal protection from 3 by formolysis for 6–10 h afforded 1-bromo-3-buten-2-one, 4, in 85–94% yield. A more rapid method is acid hydrolysis of 3 under microwave activation (100 °C, 8–10 min), by which 4 was obtained in 75% yield. Full experimental details are given.

Hydrated Rare Earth Structural Networks containing the Phenylene‐1, 2‐dioxydiacetate (PDDA) Ligand

Reaction of LnCl₃ with Na₂(PDDA) (PDDA = phenylene‐1, 2‐dioxydiacetate) in a 1 to 2 mol ratio in aqueous solution yielded [Ln₂(PDDA)₃(H₂O)₆] · 2H₂O, structurally characterized for Ln = Ce ( 1 ), Sm ( 2 ) (redetermination), Tb ( 3 ) and Y ( 4 ) in a monoclinic C2/c array, a second related structural form [orthorhombic, Pbcn] being obtained for Tb ( 5 ), Ho ( 6 ) and Er ( 7 ). The ‘domains of existence' of these two previously described forms are now extended to Ce–Dy, Y, and Eu–Er, respectively. Reaction under the same conditions for the heavier Yb³⁺ ion yielded [Yb₂(PDDA)₃(H₂O)₆]_(∞|∞) · 4H₂O ( 8 ), orthorhombic, Pbca. In the case of Ln = La the bimetallic species [NaLa(PDDA)₂(H₂O)₂]_(∞|∞) · 4H₂O ( 9 ) was obtained, while reaction of LnCl₃ with Na₂(PDDA) in a 1 to 3 mol ratio led to the isolation of the isotypic (monoclinic, P2₁/c) [NaLn(PDDA)₂(H₂O)₂]_(∞|∞) · 4H₂O) for Ln = Ce ( 10 ) and Sm ( 12 ). With the smaller Ln = Yb, the more definitively bimetallic [NaYb(PDDA)₂(H₂O)₂]_(∞|∞) · 3H₂O ( 13 ) (triclinic, P$\bar{1}$ )) was obtained, the trihydrate solvation ascribed differing from that recorded (dihydrate) in a cosynchronous report.     

Growth of Chlorella vulgaris on Sugarcane Vinasse: The Effect of Anaerobic Digestion Pretreatment

Microalgae farming has been identified as the most eco-sustainable solution for producing biodiesel. However, the operation of full-scale plants is still limited by costs and the utilization of industrial and/or domestic wastes can significantly improve economic profits. Several waste effluents are valuable sources of nutrients for the cultivation of microalgae. Ethanol production from sugarcane, for instance, generates significant amounts of organically rich effluent, the vinasse. After anaerobic digestion treatment, nutrient remaining in such an effluent can be used to grow microalgae. This research aimed to testing the potential of the anaerobic treated vinasse as an alternative source of nutrients for culturing microalgae with the goal of supplying the biodiesel industrial chain with algal biomass and oil. The anaerobic process treating vinasse reached a steady state at about 17 batch cycles of 24 h producing about 0.116 m³CH₄ kgCOD_vinasse ^?1. The highest productivity of Chlorella vulgaris biomass (70 mg l^?1 day^?1) was observed when using medium prepared with the anaerobic digester effluent. Lipid productivity varied from 0.5 to 17 mg l^?1 day^?1. Thus, the results show that it is possible to integrate the culturing of microalgae with the sugarcane industry by means of anaerobic digestion of the vinasse. There is also the advantageous possibility of using by-products of the anaerobic digestion such as methane and CO₂ for sustaining the system with energy and carbon source, respectively.     

Synthesis of New Glucosylated Porphyrins Bearing an α‐d‐Linkage

This paper presents the synthesis of two new glucosyl tritolylporphyrins in which the carbohydrate moiety is connected through a carboxymethyl glycosidic α‐D‐linkage. These compounds have been obtained by reaction between porphyrins bearing an amino function with a lactone prepared from the available disaccharide isomaltulose. The photocytotoxicity of these compounds against K562 human chronic myelogenous leukemia cells has been evaluated in comparison to Photofrin II.     

Formation of Quaternary Stereogenic Centers by Copper‐Catalyzed Asymmetric Conjugate Addition Reactions of Alkenylaluminums to Trisubstituted Enones

Alkenylaluminums undergo asymmetric copper‐catalyzed conjugate addition (ACA) to β‐substituted enones allowing the formation of stereogenic all‐carbon quaternary centers. Phosphinamine–copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β‐substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl‐ and alkyl‐substituted alkenyl nucleophiles. Moreover, alkyl‐substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu‐catalyzed ACA.