Ring‐Opening of a Bicyclo[3.2.0]hepta‐1,3‐dienyl‐cobalt(<scp>I</scp>) Complex Followed by Cycloaddition

Butenschön, Holger

doi:10.1002/anie.199010571

Cited by 16 publications

(3 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, complex 576 is unsuitable for cycloaddition reactions since the activation energy exceeds that of decomplexation of the electroneutral COD ligand . However, η 5 -(bicyclo[3.2.0]hepta-1,3-dienyl)(η 4 -tetraphenylcyclobutadiene)cobalt(I) complex ( 602 ), in which COD is replaced by less easily cleavable ligand, undergoes a cycloaddition reaction with dimethyl fumarate to afford the cycloadduct 603 in 65% yield (Scheme ). , Formation of 603 from 602 is thought to occur by ring slippage, with the hapticity of the reacting ligand changing from η 5 to η 3 . Interestingly, reaction of 602 with dimethyl maleate under similar conditions affords a mixture of 603 , 604 , and 605 (0.9:0.5:1.0) in 90% yield.…”

Section: Chemistrymentioning

confidence: 99%

Cyclobutarenes and Related Compounds

2003

View full text Add to dashboard Cite

A general method for the synthesis of cyclobutarenes involves 1,4-elimination from adjacent benzylic positions, followed by ring closure of the resulting o-quinodimethane. The earliest report in which an o-quinodimethane was implicated was the reaction of R,R,R′,R′-tetrabromo-o-xylene (4) with iodide to give the 1,2-dibromocyclobutarene 6, via o-quinodimethane 5. Treatment of 6 with NaI in acetone gave diiodide 7, which on catalytic reduction gave 1 (Scheme 1). [15][16][17] Cava and co-workers confirmed that 5 was an intermediate by trapping experiments using sev-eral dienophiles. 18 A similar procedure has been used to prepare 1,2-diphenylcyclobutarene. 19 Heterocyclic analogues may also be prepared by the 1,4-elimination of halogen from suitable precursors. Compounds 9 and 11 have been synthesized from 8 and 10, respectively, as illustrated in Scheme 2. 20 A variation of the method involves the conversion of R-alkyl-R-bromosulfones into cyclobutarenes using tetrabutylammonium fluoride (TBAF) in acetonitrile at 20-25 °C to effect the elimination. 21 The desired cyclobutarene is often accompanied by olefinic side products, as illustrated in the preparation of cyclobutarene 13, which is accompanied by 14 (eq 1) (Table 1). Anil K. Sadana was born in Panipat, India. He did his M.Sc (1990) and M. Phil (1992) from Kurukshetra University, India. He obtained his Ph.D. degree in 1999 under the guidance of Prof. Om Prakash. His Ph.D. work focused on the utility of hypervalentiodine reagents in the synthesis of heterocyclic compounds. He then joined Prof. W. E. Billups lab as postdoctoral research associate in 2000. He is presently working on small ring compounds and carbon nanotubes. Rajesh Kumar Saini was born in 1966 in Ambala, India. He received his masters degree in 1989 and his Ph.D. in 1996 from Kurukshetra University, India. After his doctorate he moved to the United States for his postdoctoral studies. After a brief stay at Sam Houston State University he joined Rice University, where he is working as a Research Scientist in the laboratories of Prof. W. E. Billups and Prof. Richard E. Smalley. His research has concentrated on small ring compound and the development of carbon nanotube chemistry. W. E. Billups was born in 1939 in Huntington, West Virginia. He received his B.S. in Chemistry Degree from Marshall University in 1961. This was followed by a period in industry after which he entered the graduate school of the Pennsylvania State University in 1968 and received the Ph.D. in 1970. He then joined the chemistry department at Rice University. He served as the Department Chair from July 1985 until December 1991. His research interests are divided among the areas of small-ring compounds, reactive intermediates, chemistry of free metal atoms and more recently fullerene and carbon nanotube chemistry.

show abstract

Section: Chemistrymentioning

confidence: 99%

Cyclobutarenes and Related Compounds

2003

View full text Add to dashboard Cite

show abstract

“…617 A comparable ring opening (Scheme 55), although at high temperature, has been found by differential scanning calorimetry in complex 387. 622,623 Above 200°C a clean caloric effect was observed which the authors associated with a (reversible) ring opening of the annelated cyclobutene ring and η 5 to η 3 hapticity change of the Cp ring (ring slippage), giving the coordinatively unsaturated 388. This assumption was verified by thermolysis of 387 at 200°C in the presence of large excesses of dimethyl fumarate, maleate, N-methylmaleimide, and diphenylacetylene as dienophiles.…”

mentioning

confidence: 99%

Metal-Assisted Cycloaddition Reactions in Organotransition Metal Chemistry

1997

View full text Add to dashboard Cite

show abstract

“…In contrast, complex 59 having a tetraphenylcyclobutadiene ligand underwent ring opening at 200 1C and further reacted with dimethyl fumarate to afford the [4 þ 2] cycloadduct 60 (Scheme 28) 32. …”

mentioning

confidence: 97%