Continuous Flow Ni- or Ru-Zeolite-Catalyzed Intramolecular Dehydration of Diols and Seco-Acids for Macrocyclic Ethers and Lactones.

Herein, we report the efficient intramolecular dehydrative coupling of symmetrical and unsymmetrical diols for the synthesis of macrocyclic crown ethers in the presence of Ni-zeolite as a catalyst under continuous flow module. This method is also efficient for the intramolecular dehydrative macrolactonization of seco-acids using Ni-zeolite or Ru-zeolite. This flow catalysis is demonstrated by a wide substrate scope with one-time packed Ni-zeolite to produce 20 macrocyclic polyethers and 11 examples of broad macrolactones with water as a byproduct.

Synthesis of Macrolactams from Macrolactones Using Ru-/Ir-Catalytic System under Neutral Conditions.

Herein, we report the Ru-/Ir-catalyzed synthesis of valuable macrolactams from macrolactones and esters. The ring-opening of the macrolactones was efficaciously facilitated by the Ru catalyst to generate 32 amides in the first step. In the second step, intramolecular -alkylative ring closure of amides with alcohols was succeeded by Ir catalyst to provide a series of 22 macrolactams and gave water as a byproduct.

Continuous Flow Inter- and Intramolecular Macrolactonization under High Dilution Conditions.

An efficient continuous flow process for the macrolactonization of seco acids and diacids using diols in the presence of Mukaiyama reagent (-methyl-2-chloropyridinium iodide) has been developed for medium to large sized macrocyclic lactones. In comparison with other methods, the continuous flow process provided good to high yield in a short reaction time. By using this methodology, a wide range of macrocyclic lactones (11 compounds), dilactones (15 compounds), and tetralactone derivatives (2 compounds) with various ring sizes (12-26 atoms in the core) were synthesized in just 35 min of residence time.

Dehydrogenative Intramolecular Macrolactonization of Dihydroxy Compounds Using Ru-MACHO Catalyst.

Herein, we have developed a new approach for the synthesis of 11 to 21-membered macrolactones via intramolecular dehydrogenative coupling of primary alcohols by using Ru-MACHO as a catalyst and CsCO as a base. This protocol generated 11-21-ring-sized macrocycles (26 derivatives), free from an external oxidant or an additive, eliminating stoichiometric reagents and producing only hydrogen as a byproduct.

Ru-MACHO-Catalyzed Direct Inter/Intramolecular Macrocyclization of Alcohols and Ketones.

Herein we describe a new approach for end-to-end cyclization to construct macrocycles through the inter/intramolecular dehydrogenative coupling of alcohols and ketones in the presence of a Ru-MACHO catalyst. This method is highly atom economical and sustainable and can be used for many substrates. Additionally, this method results in the generation of only water as the byproduct.

Catalytic Acceptorless Dehydrogenation of Amino Alcohols and 2-Hydroxybenzyl Alcohols for Annulation Reaction under Neutral Conditions.

A base-free and acceptorless Ru-catalyzed dehydrogenative approach has been developed for the synthesis of -heterocycles by using 1,3-dicarbonyls and amino alcohols through a domino sequential enamine formation and intramolecular oxidative cyclization strategy. This unified approach is also applicable for the synthesis of O-heterocycles involving 2-hydroxybenzyl alcohol as a coupling reactant via consecutive C-alkylation and intramolecular cyclization steps. The present protocol is general for the synthesis of varieties of biologically important scaffolds, such as tetrahydro-4-indol-4-one, 3,4-dihydroacridin-1(2)-one, and tetrahydro-1-xanthen-1-ones derivatives using a single catalytic system, viz.