Alcohols as Substrates in Transition-Metal-Catalyzed Arylation, Alkylation, and Related Reactions

Alcohols are abundant and attractive feedstock molecules for organic synthesis. Many methods for their functionalization require them to first be converted into a more activated derivative, while recent years have seen a vast increase in the number of complexity-building transformations that directly harness unprotected alcohols. This Review discusses how transition metal catalysis can be used toward this goal. These transformations are broadly classified into three categories. Deoxygenative functionalizations, representing derivatization of the C-O bond, enable the alcohol to act as a leaving group toward the formation of new C-C bonds. Etherifications, characterized by derivatization of the O-H bond, represent classical reactivity that has been modernized to include mild reaction conditions, diverse reaction partners, and high selectivities. Lastly, chain functionalization reactions are described, wherein the alcohol group acts as a mediator in formal C-H functionalization reactions of the alkyl backbone. Each of these three classes of transformation will be discussed in context of intermolecular arylation, alkylation, and related reactions, illustrating how catalysis can enable alcohols to be directly harnessed for organic synthesis.

Synthesis and Characterization of a Ring-Opening Oxaspiro Comonomer by a Novel Catalytic Method for Denture Base Resins

Background:

3,9-Dimethylene-1,5,7,11-tetraoxaspiro[5,5]undecane (DMTOSU) is a double ring-opening monomer that exhibits expansion upon polymerization and may be used as a denture base resin's comonomer to offset or minimize polymerization shrinkage. It's synthesis by transesterification reaction (TE) catalyzed by distannoxane is not reported in the literature. The synthesis became the prime concern because this monomer is hardly available commercially.

Purpose:

The purpose is to confirm the DMTOSU synthesis and compare the synthesized monomers obtained by two different catalytic processes through Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopies.

Materials and Methods:

Scheme I synthesis was by TE catalyzed by dichlorotetrabutyl distannoxane (DCBS) yielding M1 monomer. Scheme II synthesis was catalyzed by dibutyltin oxide-carbon disulfide (DBTO-CS₂) yielding M2 monomer.

Results:

The appearance of a characteristic peak at 1212 cm⁻¹ in FTIR spectrum, a doublet at δ 4.95 in ¹H-NMR spectrum and a peak at δ 117.12 in ¹³C-NMR spectrum confirmed the synthesis of DMTOSU-M1catalyzed by DCBS, which is not significantly different from DMTOSU-M2 catalyzed by DBTO-CS₂.

Conclusion:

The catalytic action of DCBS is a successful alternative to the DBTO-CS₂ catalysis in DMTOSU synthesis.

Biocompatible ionic liquid [Betaine][H2PO4] as a reusable catalyst for the substitution of xanthen-9-ol under solvent-free conditions

An ionic liquid, namely [Betaine][H2PO4], was found to be an efficient catalyst for the direct substitution reaction of xanthen-9-ol with different nucleophiles under solvent-free conditions. This catalytic system is easy to be operated and the following work-up procedure is simple, with the ionic liquid catalyst reusable for at least five cycles at a high catalytic activity level. In addition, the ionic liquid is easy to prepare and its raw materials are inexpensive and have good biocompatibility. Therefore, our study presents an intriguing and sustainable protocol for the direct substitution of alcohol.

Iodine-catalyzed efficient synthesis of xanthene/thioxanthene-indole derivatives under mild conditions

An iodine-catalyzed nucleophilic substitution reaction of xanthen-9-ol and thioxanthen-9-ol with indoles has been developed, providing an efficient procedure for the synthesis of xanthene/thioxanthene-indole derivatives with good to excellent yields. This protocol offers several advantages, such as short reaction times, green solvent, operational simplicity, easily available catalyst and mild reaction conditions. Moreover, this method showed good tolerance of functional groups and a wide range of substrates.