New Oxidation of β-Hydroxy α-Methyl Ketones:  A Convenient Synthesis of 3-Methylalkane-2,4-diones

Abstract

The synthesis of 3-methylalkane-2,4-diones, which are intense strawlike and fruit-flavored compounds, has been performed by the aldol condensation of n-alkanal (C2−C7) and methyl ethyl ketone to give 4-hydroxy-3-methyl-2-alkanones in 31−72% yield, followed by oxidation using sodium hypochlorite in the presence of 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-N-oxide in 60−86% yield.

Convenient syntheses of iso‐methyl‐branched long‐chain aliphatic aldehydes, known to contribute significantly to meat flavour

“…13 For the oxidation catalyst, we selected BzOTEMPO, which is more stable than TEMPO and is available from Taoka Chemical (Osaka, Japan) in industrial grades, as in our previous work. 14,15 Thus, iso-methylalkanol 2 and 1 M% BzOTEMPO in CH 2 Cl 2 were added to a mixture of 20 M% NaHCO 3 and 10 M% of an aqueous KBr solution, and then 3 Meq of 4 M/ l NaOCl was added dropwise at 5°C for 1.5 h. The reaction mixture was stirred for 3 h and checked by GC. The results of the oxidation are shown in Table 3.…”

Total Synthesis of an Antifouling Marine Furanosesquiterpene

“…Still better results were achieved by changing the base to LDA and using one equivalent of acetone in THF (entry 5). 25 Gratifyingly, these conditions worked equally well on substrate 7, providing aldol 10 in 66% yield. Subsequent oxidation to diketone 2 proceeded smoothly using stabilized IBX, 26 although the product degraded upon storage and was used immediately for the next step.…”

Cerium‐Catalyzed α‐Hydroxylation Reactions of α‐Cyclopropyl β‐Dicarbonyl Compounds with Molecular Oxygen

“…Claisen condensation of phenyl ketone 7b was more problematic, but could be achieved with benzoic anhydride after stoichiometric deprotonation with LDA. [22] However, O-acylation was the predominant process and enol ester 8 was isolated as the major product, which could be recycled to the starting material 7b in 82 % yield by saponification [23] . The new C-acylation product 1b was obtained in preparatively useful amounts by repeated conversion of ketone 7b.…”