There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

4.2.8. Reductive Coupling 3109 5. Reaction of Aromatic Compounds 3110 5.1. Electrophilic Substitutions 3110 5.2. Radical Substitution 3111 5.3. Oxidative Coupling 3111 5.4. Photochemical Reactions 3111 6. Reaction of Carbonyl Compounds 3111 6.1. Nucleophilic Additions 3111 6.1.1. Allylation 3111 6.1.2. Propargylation 3120 6.1.3. Benzylation 3121 6.1.4. Arylation/Vinylation 3121 6.1.5. Alkynylation 3121 6.1.6. Alkylation 3121 6.1.7. Reformatsky-Type Reaction 3122 6.1.8. Direct Aldol Reaction 3122 6.1.9. Mukaiyama Aldol Reaction 3124 6.1.10. Hydrogen Cyanide Addition 3125 6.2. Pinacol Coupling 3126 6.3. Wittig Reactions 3126 7. Reaction of R,â-Unsaturated Carbonyl Compounds 3127

Organic Reactions in Aqueous Media with a Focus on Carbon−Carbon Bond Formations: A Decade Update

Asymmetric multicomponent reactions involve the preparation of chiral compounds by the reaction of three or more reagents added simultaneously. This kind of addition and reaction has some advantages over classic divergent reaction strategies, such as lower costs, time, and energy, as well as environmentally friendlier aspects. All these advantages, together with the high level of stereoselectivity attained in some of these reactions, will force chemists in industry as in academia to adopt this new strategy of synthesis, or at least to consider it as a viable option. The positive aspects as well as the drawbacks of this strategy are discussed in this Review.

Asymmetric multicomponent reactions (amcrs): the new frontier

Stereoselective organic reactions in water.

Functional π-Gelators and Their Applications

Synthesis of 3-Substituted Pentane-2,4-Diones: Valuable Intermediates For Liquid Crystals

This review describes available methods for the preparation of α-aminoboronic acids in their racemic or in their enantiopure form. Both, highly stereoselective syntheses and asymmetric procedures leading to the stereocontrolled generation of α-aminoboronic acid derivatives are included. The preparation of acyclic, carbocyclic and azacyclic α-aminoboronic acid derivatives is covered. Within each section, the different synthetic approaches have been classified according to the key bond which is formed to complete the α-aminoboronic acid skeleton.

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Synthesis of α-aminoboronic acids

S.S. acknowledges CSIR, New Delhi, India, for SRF. R.B. acknowledges CSIR, DST, and BRNS for funding. D.D.D. acknowledges CSIC (project PIE 200980I059) and the University of Regensburg (Anschubfinanzierung von Wissenschaftlichen Projekten-2011) for funding. C.C. acknowledges CC Ministerio de Ciencia e Innovacion—FEDER (project CTQ2010–17436) for funding.

Proton‐Conducting Supramolecular Metallogels from the Lowest Molecular Weight Assembler Ligand: A Quote for Simplicity

Rate, endo/exo, regio- and diastereo-facial selectivities of several Diels–Alder reactions were measured in a
series of fluorinated alcohol–water mixtures, whose solvophobicity has been determined by means of the
solvophobic power (Sp) parameter. Solvophobicity is the main factor influencing the reaction rate,
although in some reactions hydrogen bond donating (HBD) ability may also play a role. Both
solvophobicity and HBD ability are important to account for changes in endo/exo selectivity. HBD ability
is the main factor responsible for the changes in regio- and diastereo-facial selectivities, induced by the
reaction medium. On the other hand, the kinetic rate constants and endo/exo selectivity of the reaction of
acrylonitrile with cyclopentadiene, as well as the regioselectivity of the reaction of acrylonitrile with
isoprene, have been determined in 23 reaction media. The analysis of the results using empirical solvent
parameters show that the reaction rate depends on solvophobic, HBD and dipolarity interactions, whereas
endo/exo selectivity is influenced by solvophobic and dipolarity interactions, and the regioselectivity only
by HBD effects.

Solvent effects on Diels-Alder reactions. the use of aqueous mixtures of fluorinated alcohols and the study of reactions of acrylonitrile

The model dipeptides RCO-l-Pro-c3Phe-NHMe, where c3Phe stands for each of the four cyclopropane analogues of phenylalanine (2,3-methanophenylalanine), have been studied in solution by using 1H NMR and FT-IR spectroscopy and in the solid state by using X-ray diffraction. The conformational behavior of these compounds has been compared to that of the analogous Ac3c and l- or d-Phe-containing dipeptides. When associated to proline, the cyclopropane residues in the so-called i + 2 position exhibit a marked tendency to β-folding in solution, even in DMSO. The type II β-turn is generally favored, but the βI/βII-turn ratio depends both on the experimental conditions (solvent, solution, or solid state) and on the chirality of the c3Phe moiety, which rigidly fixes the orientation of the phenyl ring with respect to the peptide backbone. The (2S,3S)c3Phe residue, analogous to l-Phe with the χ1 angle constrained to about 0°, is the most propitious to βI-folding in the i + 2 position of a putative β-turn.

Carlos Cativiela

Papers

Synthesis of 3-Substituted Pentane-2,4-Diones: Valuable Intermediates For Liquid Crystals

Synthesis of α-aminoboronic acids

Proton‐Conducting Supramolecular Metallogels from the Lowest Molecular Weight Assembler Ligand: A Quote for Simplicity

Solvent effects on Diels-Alder reactions. the use of aqueous mixtures of fluorinated alcohols and the study of reactions of acrylonitrile

β-Turn Preferences Induced by 2,3-Methanophenylalanine Chirality†