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Diastereoselective Synthesis of Five‐ and Seven‐Membered Rings by [2+2+1], [3+2], [3+2+2], and [4+3] Carbocyclization Reactions of β‐Substituted (Alkenyl)(methoxy)carbene Complexes with Methyl Ketone Lithium Enolates
Author(s) -
Barluenga José,
Alonso Jorge,
Fañanás Francisco J.
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200500164
Subject(s) - ketone , carbene , lithium (medication) , chemistry , aryl , acetone , medicinal chemistry , ether , alkyl , organic chemistry , catalysis , endocrinology , medicine
β‐Substituted alkenylcarbene complexes react with methyl ketone lithium enolates to give different carbocyclization products depending on the structure of the lithium enolate, on the metal of the carbene complex, and on the reaction media. Thus, the reactions of aryl and alkyl methyl ketone lithium enolates with β‐substituted alkenyl chromium and tungsten carbene complexes in diethyl ether afford 1,3‐cyclopentanediol derivatives derived from a formal [2+2+1] carbocyclization reaction. However, the lithium enolates of acetone and tungsten complexes furnish formal [3+2+2] carbocyclization products. In the case of alkynyl methyl ketone lithium enolates, competitive formal [2+2+1] and [3+2] carbocyclization reactions occur and 1,3‐cyclopentanediol and 3‐cyclopentenol derivatives are formed. Conversely, alkenyl methyl ketone lithium enolates react with alkenylcarbene complexes under the same reaction conditions to form 2‐cycloheptenone derivatives by a formal [4+3] carbocyclization reaction. Finally, when the reaction was performed in the presence of a coordinating medium, the [3+2] carbocyclization pattern was observed independently of the nature of the methyl ketone lithium enolate used.