Synthesis 2021; 53(04): 699-712
DOI: 10.1055/s-0040-1707322
paper

Inter- and Intramolecular [2+2+2] Cycloaddition of Alkyne Triple Bonds to the Carbonyl Function of Aldehydes and Ketones Enabled by η5-Cyclopentadienylcobalt(L)(L′)

Véronique Colovray-Gotteland
,
Daniel F. Harvey
,
Barry M. Johnson
,
Christopher S. Ung
,
This work was funded by the National Institutes of Health (NIH, GM 22479), the National Science Foundation (NSF, CHE 0907800), and the University of California at Berkeley.


Zoom Image

Abstract

1,7-Octadiyne underwent [2+2+2] cycloaddition to acetone in the presence of η5-cyclopentadienylcobalt(L)(L′) complexes to give (η5-cyclopentadienyl)[(1,4,4a,8a-η4)-5,6,7,8-tetrahydro-3,3-dimethyl-3H-2-benzopyran]cobalt, in which the two triple bonds and the carbonyl moiety have combined to engender a 2H-pyran ring complexed to CpCo. The scope of this reaction was explored, including cocyclizations of ynals and ynones with bis(trimethylsilyl)acetylene, as well as all-intramolecular reorganizations of α,ω-diynals and -diynones. Two major trajectories were observed in the case of aldehydes, the (often minor) [2+2+2] pathway and a competing trail featuring a formal 1,5-hydride shift that results in CpCo–dienones. The latter is obviated for ketone substrates. Preliminary chemistry of selected complexes uncovered unprecedented reactions, such as acid-catalyzed ring openings and additions of amines, the latter providing access to novel carbon frames.

Supporting Information



Publication History

Received: 07 September 2020

Accepted after revision: 14 September 2020

Article published online:
12 October 2020

© 2020. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany