The Synthesis and Some Reactions of Diazocyclobutane<sup>1</sup>

Applequist, Douglas E.; McGreer, Donald E.

doi:10.1021/ja01493a032

Cited by 30 publications

(15 citation statements)

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“…20 Study of 1,3 dipolar cycloaddition reactions. Our ex perimental studies 7-9 have demonstrated that, in spite of the low dissociation energy, diazocyclopropane (1) exists as a highly labile compound.…”

Section: Resultsmentioning

confidence: 99%

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

et al. 2005

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The electronic structures and dissociation energies of diazocyclopropane (1), diazo methane (2), 2 diazopropane (3), and diazocyclobutane (4) were calculated at the density functional B3LYP and the ab initio MP2 levels using the 6 31G(d) basis set and at the G2(MP2,SVP)//B3LYP/6 31G(d) level. Distinctive features of diazocyclopropane 1 are the low energy of dissociation with loss of the nitrogen molecule; ∆E = 18.7 kcal mol -1 , B3LYP; 9.2 kcal mol -1 , G2 at 0 K) and a nonplanar structure, in which the C=N bond forms an angle of 115.7° with the plane of the cyclopropane ring. The behavior of molecules 1 and 2 in the 1,3 dipolar cycloaddition to ethylene (5), acrylonitrile (6), and methyl acrylate (7) was stud ied. The reactions of 1 with 6 and 7 have very low activation barriers (∆E a = 4.7 and 4.4 kcal mol -1 , respectively; at the B3LYP level). For these reactions, the G2 method gives even smaller activation parameters (1.8 and 0.3 kcal mol -1 , respectively). The results of our calculations provide a good explanation for high reactivity of diazocyclopropane 1.The characteristic feature of diazo compounds is their ability to react as 1,3 dipoles in [3+2] cycloaddition re actions with unsaturated compounds. Such reactions are well studied both experimentally and theoretically. 1 The reaction mechanisms of cycloaddition 2-4 and the regio selectivity 5,6 of the process were studied in depth by mod ern quantum chemical methods. We found that diazo cyclopropane (1) is distinguished from a whole series of aliphatic diazo compounds by high reactivity. 7Diazocyclopropane (1) is very unstable and remains undetectable by spectroscopic methods. However, when generated in situ in the presence of appropriate trapping agents, compound 1 can give the corresponding trapping products in preparative yields. These reactions afford pyrazolines containing the spiro fused cyclopropane frag ment (Scheme 1). Scheme 1 B is a baseDiazocyclopropane 1 is most efficiently trapped by substrates in which the C=C bond is elongated due to the presence of a strained hydrocarbon moiety 8 or is conju gated with electron withdrawing groups. 9 Attempts to pre pare addition products of compound 1 to substrates con taining an inactivated double bond (for example, to alk 1 enes) failed. In this case, reactions involving the ini tial dediazotization of diazocyclopropane 1 play the main role. 10 The hypothesis of a nonplanar structure of diazo cyclopropane 1, which has been put forward more than 40 years ago, 10 is a possible key to understanding the unusual behavior of this compound. The nonplanar struc ture of 1 is also supported by the results of quantum chemi cal calculations at the RHF/6 31G(d) level of theory. 11 However, the geometric structure of diazocyclopropane has not been described in the latter study.To elucidate the geometric features and the electronic structure of molecule 1 and explain its chemical proper ties, we carried out quantum chemical calculations by the B3LYP, MP2, and G2 methods. ExperimentalQuantum chemical calculations of ...

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Section: Resultsmentioning

confidence: 99%

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

et al. 2005

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“…[*] Dr.A.Greb, [ Using an umber of oxadiazolines and readily available boronic acids (forming boroxines in situ), [13] we were able to demonstrate ar emarkably broad reaction scope and unusually high functional-group compatibility (Table 1). With respect to the oxadiazoline component, av ariety of pharmaceutically relevant 4-, 5-and 6-membered saturated heterocyclic examples were viable coupling partners,i ncluding pyran (3a), tetrahydrofuran (3b), tetrahydrothiopyran (3c), tetrahydrothiophene (3d), thietane (3e), N-Boc piperidine (3f), N-Boc pyrrolidine (3g), and N-Boc azetidine (3h)rings, providing moderate to excellent yields of the desired C(sp 2 )À C(sp 3 )c ross-coupling products.I ti sp articularly notable that the 4-membered rings were viable examples given the instability of 4-membered cyclic diazo compounds, [14] which arises from the relief of ring strain when moving from an sp 2 to an sp 3 carbon center on reaction with electrophiles. Furthermore,t olerance of the tetrahydrothiophene and thietane moieties highlights examples where approaches using at osylhydrazone route or carbon-centered radical approaches would fail, due to the tendency of these systems to undergo elimination/ring-opening.Anumber of carbocyclic examples containing cycloalkyl groups (3i-3l)w ere also permissible substrates,along with ahighly hindered adamantane substituent (3m).…”

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A Versatile Route to Unstable Diazo Compounds via Oxadiazolines and their Use in Aryl–Alkyl Cross‐Coupling Reactions

et al. 2017

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Coupling of readily available boronic acids and diazo compounds has emerged recently as a powerful metal‐free carbon–carbon bond forming method. However, the difficulty in forming the unstable diazo compound partner in a mild fashion has hitherto limited their general use and the scope of the transformation. Here, we report the application of oxadiazolines as precursors for the generation of an unstable family of diazo compounds using flow UV photolysis and their first use in divergent protodeboronative and oxidative C(sp2)−C(sp3) cross‐coupling processes, with excellent functional‐group tolerance.

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“…Similarly to the cyclobutyl hydrazone, the related cyclooctyl gave a still acceptable but lower yield of 61% of the corresponding product 8k . These lower yields are believed to be due to the higher instability of the diazo compounds 26. Non-symmetrical hydrazones were then tested.…”

Section: Resultsmentioning

confidence: 99%

Non-stabilized diazoalkane synthesis via the oxidation of free hydrazones by iodosylbenzene and application in in situ MIRC cyclopropanation

Allouche

Charette

2019

Chem. Sci.

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The Synthesis and Some Reactions of Diazocyclobutane¹

Cited by 30 publications

References 1 publication

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

A Versatile Route to Unstable Diazo Compounds via Oxadiazolines and their Use in Aryl–Alkyl Cross‐Coupling Reactions

Non-stabilized diazoalkane synthesis via the oxidation of free hydrazones by iodosylbenzene and application in in situ MIRC cyclopropanation

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The Synthesis and Some Reactions of Diazocyclobutane1

Cited by 30 publications

References 1 publication

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

Comparative quantum chemical investigation of structures and properties of diazocyclopropane and other diazoalkanes

A Versatile Route to Unstable Diazo Compounds via Oxadiazolines and their Use in Aryl–Alkyl Cross‐Coupling Reactions

Non-stabilized diazoalkane synthesis via the oxidation of free hydrazones by iodosylbenzene and application in in situ MIRC cyclopropanation

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The Synthesis and Some Reactions of Diazocyclobutane¹