Synthesen ausgehend von 1-Methoxybuten( 1)-in(3)

Starting with 1-methoxy-butene(l)-in(3) there are two possibilities for the synthesis of longchained [alpha], [beta]-unsaturated aldehyd-acetales. Both ways are described. The first involves the formation of the C-C-linkage by application of the acetylene-Grignard-synthesis, followed by partial hydrogenation. The second begins with the hydrogenation to 1-methoxy-butadiene, followed by methoxy-bromination to [gamma]-bromo-crotonaldehyde-acetal and its condensation with alkali-metalorganic compounds as sodium malonicester or alkali cyanide

Über den Schutz von Hydroxylgruppen in optisch aktiven Alkoholen

Optical active alcohols can be protected by preparing acetales. Cleavage is possible as shown with L-menthol without racemisation of the active compound

Discerning the thermal cyclotrimerizations of fluoro- and chloroacetylenes through ELF, NBO descriptors and QTAIM analysis: pseudodiradical character

In this study the thermal cyclotrimerization reactions of fluoro- and chloroacetylenes involving regioselectively stepwise {2 + 2} and stepwise {4 + 2} cycloadditions were studied using the topological analysis of the electron localization function (ELF), the quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analyses. These methodologies have shown that the electronic reorganization in the regioselectively stepwise {2 + 2} and stepwise {4 + 2} cycloadditions may be considered as {2n + 2n} and {2 pi + 2n} pseudodiradical process,respectively. Finally, the last phase of this thermal reaction can be understood as an electronic migration process under the pseudodiradical character in the thermal ring-opening reaction, with the subsequent formation of reactionproducts. In this sense, new insights are reported on the electronic behavior in the bond formation in the thermal cyclotrimerization of fluoroacetylene

Radical reaction control in the AdoMet radical enzyme CDG Synthase (QueE): consolidate, destabilize, accelerate

Controlling radical intermediates and thus catalysing and directing complex radical reactions is a central feature of S-adensosylmethionine (SAM)-dependent radical enzymes. We report ab initio and DFT calculations highlighting the specific influence of ion complexation, including Mg2+, identified as a key catalytic component on radical stability and reaction control in 7-carboxy-7-deazaguanine synthase (QueE). Radical stabilisation energies (RSEs) of key intermediates and radical clock-like model systems of the enzyme-catalysed rearrangement of 6-carboxytetrahydropterin (CPH4), reveals a directing role of Mg2+ in destabilising both the substrate-derived radical and corresponding side reactions, with the effect that the experimentally-observed rearrangement becomes dominant over possible alternatives. Importantly, this is achieved with minimal disruption of the thermodynamics of the substrate itself, affording a novel mechanism for an enzyme to both maintain binding potential and accelerate the rearrangement step. Other mono and divalent ions were probed with only dicationic species achieving the necessary radical conformation to facilitate the reaction

Sodium Tertiary Pentoxide: A Mild and Efficient Base to Make C-C Bond between Acetylenes and Aldehydes (or) Ketones Producing Propargyl Alcohols

This report confirms that sodium tertiary‐pentoxide is a very effective base for the nucleophilic addition of acetylenes to aldehydes and ketones in 1,4‐dioxane at room temperature. These mild and operationally simple procedures have been working well with a variety of aromatic and heteroaromatic aldehydes and also equally working well with aliphatic, aromatic and heteroaromatic ketones. A very clean product of secondary and tertiary propargylic alcohols were obtained from 70–94% yield. This process has been explored in bulk scale synthesis on selected molecules and also adapted the column free purification for most of the substrates