Technological Aspects of Highly Selective Synthesis of Allyloxyalcohols—New, Greener, Productive Methods

Allyl ethers bearing free hydroxyl groups of CH2=CH-CH-O-A-OH type (hydroxyalkyl allyl ethers, allyloxyalcohols) are valuable chemicals in many environmentally friendly industrial applications. The development of technologically attractive methods for their production is necessary. The two pathways (L-L PTC and non-catalytic solvent-free conditions) were optimized for the highly selective and yield synthesis of 4-allyloxybutan-1-ol. Improvements in the PTC method (50% NaOH(aq), the equimolar ratio of NaOH to diol, cyclohexane as solvent) with a new highly selective and effective PT catalyst, i.e., Me(n-Oct)3N+Br− (0.3 mol%), resulted in 88% yield and 98% selectivity of 4-allyloxybutan-1-ol with minimal formation of allyl chloride hydrolysis by-products (<1%). In turn, application of non-catalytic solvent-free conditions and the change in the key substrate with an excess of diol and use of solid NaOH solely led to a mono-O-allylation product with an excellent yield of 99% in a relatively short reaction time (3.5 h), with trace amounts of by-products (<0.1%). This sustainable method is perfectly suitable for the synthesis on a larger scale (3 moles of the key substrate) and for the full O-allylation process.

Transition-metal-free allylation of 2-azaallyls with allyl ethers through polar and radical mechanisms

Allylation of nucleophiles with highly reactive electrophiles like allyl halides can be conducted without metal catalysts. Less reactive electrophiles, such as allyl esters and carbonates, usually require a transition metal catalyst to facilitate the allylation. Herein, we report a unique transition-metal-free allylation strategy with allyl ether electrophiles. Reaction of a host of allyl ethers with 2-azaallyl anions delivers valuable homoallylic amine derivatives (up to 92%), which are significant in the pharmaceutical industry. Interestingly, no deprotonative isomerization or cyclization of the products were observed. The potential synthetic utility and ease of operation is demonstrated by a gram scale telescoped preparation of a homoallylic amine. In addition, mechanistic studies provide insight into these C(sp3)–C(sp3) bond-forming reactions.

Selective Transfer of Si Thin-Film Microchips by SiO2 Terraces on Host Chips for Fluidic Self-Assembly

Fluidic self-assembly is a versatile on-chip integration method. In this scheme, a large number of semiconductor microchips are spontaneously deposited onto a host chip. The host chip typically comprises a Si substrate with an array of pockets at the designated microchip placement sites. In this study, we installed an SiO2 layer on the terrace region between the pockets of the host chip, to reduce the attraction with the Si microchips. By the SiO2-topped terrace scheme, we demonstrated a significant enhancement in the deposition selectivity of the Si microchips to the pocket sites, relative to the case of the conventional Si-only host chip. We theoretically explained the deposition selectivity enhancement in terms of the van der Waals interaction. Furthermore, our quantitative analysis implicated a potential applicability of the commonly used interlayer dielectrics, such as HfO2, silsesquioxanes, and allyl ethers, directly as the terrace component.

Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization

This report discloses the deallylation of O- and N-allyl functional groups by using a combination of a Ni-H precatalyst and excess Brønsted acid. Key steps are the isomerization of the O- or N-allyl group through Ni-catalyzed double-bond migration followed by Brønsted acid induced O/N–C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.

A Mild and Practical Method for Deprotection of Aryl Methyl/ Benzyl/Allyl Ethers with HPPh2 and tBuOK

A general method for the demethylation, debenzylation, and deallylation of aryl ethers using HPPh2 and tBuOK is reported. The reaction features mild and metal-free reaction conditions, broad substrate scope, good...

Substantiation of the Erdenetiyn-Ovoo copper-molybdenum ore flotation technology with the use of tertiary acetylene alcohol

The article presents the results of a study of the factors affecting the efficiency of the copper-molybdenum ore flotation. The objective of this work was to substantiate and develop a reagent mode for flotation of the Erdenetiyn-Ovoo porphyry copper ores, which makes possible extracting main copper and molybdenum minerals into corresponding concentrates more fully and selectively. It is shown that the use of a DC-80 (2-methyl-3-butin-2-ol) flotation reagent in assosiation with the main base mode reagents — an AERO MX-5152 (a mixture of allyl ethers of xanthogenic acids with n-butyloxycarbonyl-O-n-butylthionocarbamate) combined nonionized collector, a BK-901B (a composition of dialkyldithiophosphate and O,N-dialkyldithiocarbamate) blending ionized collector; diesel fuel; a MIBC (methyl isobutyl carbinol) frother; sodium sulphide Na2S as a modifier and lime СаО as a pH regulator of the medium allows obtaining a noticeable, economically sound additional recovery of both copper and molybdenum. Quantum chemical calculations have permitted to establish an important feature of the mechanism of interaction between the DC-80 molecules that can form stronger complexes based on -bonds with metal cations of sulfide minerals in comparison with allyl ethers of xanthogenic acids. The energy indicators of the formation of bonds between Cu2S, the DC-80 molecules and allyl ether of xanthic acid were calculated. There were shown the models of the assumed interaction of small mineral particles with air bubbles during flotation, which are determined by physical and chemical properties of the molecules of acetylene-containing reagents. The principal difference between the properties of the foam bubbles formed by acetylene-containing molecules for at least 50% and that of the ordinary foam bubbles formed by standard frothers has been demonstrated in the view of the mechanism of their fixing on the surface of small particles of sulfide minerals and the surface of the bubbles. The optimal flotation mode, comprising a DC-80 reagent, BK-901B and AERO MX-5152 base collectors has been developed. The application of this mode will allow increasing the copper and molybdenum recovery into concentrates by 0.62% and 5.76%, respectively, reducing the flotation time by 35–40%, and improving the quality of resulting concentrates. Based on the research results, it is recommended to incorporate the DC-80 acetylene reagent into the basic flotation mode for conducting pilot tests at the Erdenet Mining Corporation enterprises (Mongolia).