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On the syntheses of branched saturated fatty acids
Author(s) -
Gronowitz Salo,
Klingstedt Tomas,
Svensson Leif,
Hansson Ulf
Publication year - 1993
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02537496
Subject(s) - chemistry , organic chemistry , fatty acid , hydrolysis , alkylation , flue gas desulfurization , raney nickel , reagent , yield (engineering) , catalysis , materials science , metallurgy
In order to investigate the relation between the structure of mono‐branched saturated fatty acids and their physical properties, a three‐factor central composite design was constructed. For this purpose sixteen different fatty acids were prepared. The synthetic strategy was to use if possible, a few common starting materials for the preparation of most of the acids. Thus alkylation and hydrolysis of oxazolines were used for the preparation of 2‐butylhexanoic acid, 2‐methyloctadecanoic acid, 2‐hexadecyloctadecanoic acid and 2‐pentyloctadecanoic acid. A number of acids were prepared from thiophene derivatives followed by desulfurization with Raney‐Nickel alloy under alkaline conditions. Thus, starting from 3‐ethylthiophene, 4‐ethyl‐2‐thiophenecarboxylic acid and 4‐ethyl‐2‐methyl‐5‐thiophenecarboxylic acid were prepared, which upon desulfurization gave the desired 4‐methylhexanoic acid. From 3‐bromo‐2‐methylthiophene, 3‐ethyl‐2‐methyl‐5‐thiophenecarboxylic acid was prepared via 3‐acetyl‐2‐methylthiophene and 3‐ethyl‐2‐methylthiophene. Desulfurization gave 4‐ethylhexanoic acid. Another approach started with 2‐acylthiophenes, which were reacted with Grignard reagent to yield the appropriate olefins. By metalation and reaction with carbon dioxide, these were transformed to the corresponding 2‐thiophenecarboxylic acids. Upon desulfurization, the desired fatty acids were obtained. In this way 6‐propyldecanoic acid, 6‐hexyldodecanoic acid, 6‐methyldodecanoic acid and 6‐pentylpentadecanoic acid were prepared. The remaining four acids were prepared from some of the branched acids described above through Kolbe reactions of dioic acids. Thus 16‐methyloctadecanoic acid and 10‐methyl‐dodecanoic acid were obtained from 4‐methylhexanoic acid, 16‐ethyloctadecanoic acid from 4‐ethylhexanoic acid and 9‐pentyloctadecanoic acid from 6‐pentylpentadecanoic acid.