Synthesis 2016; 48(12): 1880-1891
DOI: 10.1055/s-0035-1561591
special topic
© Georg Thieme Verlag Stuttgart · New York

Organocatalyzed Microwave-Assisted Competing Cyclization of Cyanopropargylic Alcohols with Carboxylic Acids: 4-Cyano-3(2H)-furanones versus 4-Cyano-[(Z)-3-cyanomethylene]-2,3-dihydro­furans

Anastasiya G. Malkina
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Anton V. Stepanov
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Lyubov N. Sobenina
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Olesya A. Shemyakina
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Igor A. Ushakov
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Vladimir I. Smirnov
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
,
Boris A. Trofimov*
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033, Irkutsk, Russian Federation   eMail: boris_trofimov@irioch.irk.ru
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Publikationsverlauf

Received: 28. Januar 2016

Accepted after revision: 01. März 2016

Publikationsdatum:
14. April 2016 (online)


Abstract

It is shown for the first time that the reaction of cyanopropargylic alcohols with carboxylic acids in the presence of triethylamine (5–100 mol%) under microwave irradiation (MeCN, 100 °C, 1.2 atm) follows two competing pathways to afford 4-cyano-3(2H)-furanones (1:1 adduct) and 4-cyano-[(Z)-3-cyanomethylene]-2,3-dihydrofurans (2:1 adduct) in moderate to good yields. The ratio of the products depends on both the reaction conditions (the reactant ratio, catalyst content) and the reactant structure, the 2:1 adduct formation being favored by an excess of cyanopropargylic alcohol, lower catalyst content, and bulky substituents at the carboxylic functions. Both competing reactions proceed via the same intermediates, keto esters, which either intramolecularly cyclize to the 1:1 adducts, or intermolecularly add the second molecule of cyanopropargylic alcohol to give the 2:1 adducts.

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