Tetrapropylammonium Perruthenate Catalyzed Glycol Cleavage to Carboxylic (Di)Acids

Abstract

A new method to accomplish glycol cleavage to carboxylic (di)acids in one step using catalytic amounts of tetrapropylammonium perruthenate (TPAP) together with N-methylmorpholine N-Oxide (NMO) as the stoichiometric oxidant is presented. In addition to regenerating the active catalyst, the N-oxide stabilizes intermediary carbonyl hydrates and thereby shifts a crucial equilibrium. The mild oxidation protocol is applicable to a broad range of substrates providing the respective acids, diacids, or keto acids in high yields.

A Concise Total Synthesis of Amphidinin B

“…NMO•H 2 O, CH 2 Cl 2 , r.t., 24 h) reported by Stark and Schmidt [13] with failure. Initially, we attempted direct conversion of the diols into amphidinin B using the conditions (20 mol% TPAP, 2 equiv.…”

“…The optical rotation of 13 is The 1 H NMR and 13 C NMR spectra of the naturally occurring and our synthetic amphidinin B (1) recorded in C 6 D 6 and CDCl 3 are illustrated in Figures 1-3. On the other hand, the two 13 C NMR spectra given in Figure 3 are identical but intensity of the two C＝O signals in the downfield (δ 182.4 and 177.4 ) is very weak for Yadav's sample of 1 (not shown), [3] indicating that the two carboxylic acid residues in amphidinin B might be engaged in strong intermolecular interactions. In particular, the peak lines in the δ 2.8-2.0 region of the 1 H NMR spectrum of our sample are clearly resolved (Figure 1a), allowing assignment of the coupling constants.…”

ATP3 and MTP3: Easily Prepared Stable Perruthenate Salts for Oxidation Applications in Synthesis

“…Our own TPAP reactivity modifications, and tandem reactions, proceeded with 16 and 19 in high yield and with minimal variation (entries 2–5 Table ). Application of Stark's method of carboxylic acid synthesis and diol cleavage proceeded in good yield with a lower yield than that with TPAP for the carboxylic acid synthesis and similar yield for the diol cleavage (entries 6 and 7 Table ). Tetrahydrofuran synthesis from geraniol acetate proceeded with higher yields with 16 and 19 than that reported with TPAP .…”

“…However, beyond basic alcohol oxidation, numerous applications for TPAP exist in synthesis . For example, diol cleavage to give dialdehydes or dicarboxylic acids, oxidation of secondary amines to imines, sulfides to sulfones, and hydroxyamines to nitrones . Additional examples include one‐pot hydroboration–oxidation of alkenes, conversion of ethers to esters, double bond isomerization, and the formation of heterocyclic ring systems, such as tetrahydrofurans, pyridines, triazoles, lactams and lactones…”

“…avoid repetitive synthesis/purchase of TPAP). CCDC 1590462 (13), 1590463 (15), 1590464 (16), 1590465 (17), 1590466 (19), and 1590467 (21)c ontain the supplementary crystallographic data for this paper.T hese data can be obtained free of chargef rom The Cambridge Crystallographic Data Centre.…”