Chemistry:Cyclobutenone
Cyclobutenone is a chemical compound with the formula C
4H
4O. It is a highly strained cyclic enone which exhibits significant chemical reactivity. Notable reactions of cyclobutenone include acting as a Michael acceptor, a dienophile for Diels-Alder reactions, and a regioselective substrate for activation of C–C bonds. Electrocyclic ring opening of cyclobutenones yields vinylketenes, which serve as reactive intermediates in cycloaddition reactions.[1]
Preparation
Unsubstituted cyclobutenone can be prepared by dehydrohalogenation of 3-bromocyclobutanone. The bromocyclobutanone precursor can be prepared by decarboxylation of 3-oxocyclobutanecarboxylic acid with bromine and mercury(II) oxide.[2]
Substituted cyclobutenones can be prepared by cycloaddition of an alkyne and ketene, such as the [2+2] cycloaddition of 1-hexyne and dichloroketene (generated in situ from trichloroacetyl chloride) to 3‑butyl‑4,4‑dichlorocyclobutenone.[3]
Reactivity
Cyclobutenone has been described as an "unusually reactive" dienophile, substantially more reactive than other enone rings like cyclopentenone and cyclohexenone.[4]
Sources
- ↑ Chen, Peng-hao; Dong, Guangbin (2016). "Cyclobutenones and Benzocyclobutenones: Versatile Synthons in Organic Synthesis". Chemistry – A European Journal 22 (51): 18290–18315. doi:10.1002/chem.201603382. PMID 27620805.
- ↑ Audrey G. Ross, Xiaohua Li, and Samuel J. Danishefsky (2012). "Preparation of cyclobutenone". Organic Syntheses 89: 491-500. http://www.orgsyn.org/demo.aspx?prep=v89p0491.
- ↑ Rick L. Danheiser, Selvaraj Savariar, and Don D. Cha. (1990). "3-Butylcyclobutenone". Organic Syntheses 68: 32. http://www.orgsyn.org/demo.aspx?prep=CV8P0082.
- ↑ Paton, Robert S.; Kim, Seonah; Ross, Audrey G.; Danishefsky, Samuel J.; Houk, K. N. (2011). "Experimental Diels–Alder Reactivities of Cycloalkenones and Cyclic Dienes Explained through Transition-State Distortion Energies". Angewandte Chemie International Edition 50 (44): 10366–10368. doi:10.1002/anie.201103998. PMID 21910195.
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