A Novel Preparation of the 1,3-Benzoxazepine Ring System

Katritzky, Alan R.; Rubio, Olga; Awartani, Radi; Latif, N.; Mishriky, N.; Assad, F. M.

doi:10.3987/r-1984-05-1155

Cited by 7 publications

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“…However, it was reported that DCM and pyridine formed compound 3a under increased temperature and pressure; the reaction was not observed at atmospheric pressure or room temperature, and an intermediate pyridinium adduct was never isolated . As might be expected, dibromomethane and diiodomethane show higher reactivity toward pyridine and its derivatives, and adducts from those have been reported. − In addition, unsymmetrical bispyridinium derivatives have been synthesized by independently reacting a halomethyl pyridinium derivative with a dissimilar pyridine …”

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“…21 As might be expected, dibromomethane and diiodomethane show higher reactivity toward pyridine and its derivatives, and adducts from those have been reported. [21][22][23] In addition, unsymmetrical bispyridinium derivatives have been synthesized by independently reacting a halomethyl pyridinium derivative with a dissimilar pyridine. 24 Since so little is known about the reaction of DCM with pyridines under ambient conditions we investigated a series of pyridine derivatives in order to determine the generality of the reaction and reactivity patterns.…”

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Reaction of Dichloromethane with Pyridine Derivatives under Ambient Conditions

2010

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Pyridine derivatives and dichloromethane (DCM) are commonly used together in a variety of different applications. However, DCM slowly reacts with pyridine and a variety of other representative pyridine derivatives to form methylenebispyridinium dichloride compounds under ambient conditions. The proposed mechanism (two consecutive S(N)2 reactions) was studied by evaluating the kinetics of the reaction between 4-(dimethylamino)pyridine and DCM. The second-order rate constants for the first (k(1)) and second (k(2)) substitutions were found to be 2.56(+/-0.06) x 10(-8) and 4.29(+/-0.01) x 10(-4) M(-1) s(-1), respectively. Because the second substitution is so much faster than the first, the monosubstitution product could not be isolated or detected during the reaction; it was synthesized independently in order to observe its kinetics.

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Reaction of Dichloromethane with Pyridine Derivatives under Ambient Conditions

2010

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“…An intramolecular version of the N -interrupted Nef/Meyer reaction was reported by Katritzky et al ( Scheme 19 ) [ 80 ]. Here, heating of nitromethyl-substituted benzoxazinones 51 with HCl/dioxane results in their rearrangement to 1,3-benzoxazepines 52 in moderate yields.…”

Section: Interruption Of the Nef And Meyer Reactions By N ...mentioning

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Interrupted Nef and Meyer Reactions: A Growing Point for Diversity-Oriented Synthesis Based on Nitro Compounds

Sukhorukov

2023

Molecules

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The Nef reaction (nitro to carbonyl group conversion) and related Meyer reaction are among the key transformations of aliphatic nitro compounds. The interrupted versions of these reactions in which the normal pathway is redirected to a different end product by an external nucleophile are much less common, albeit these processes substantially increase the synthetic potential of nitro compounds. In this review, examples of interrupted Nef and Meyer reactions are summarized, and the prospects of this methodology in diversity-oriented organic synthesis are analyzed. The bibliography contains 90 references.

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“…A central methylene to which is attached two positively charged pyridinium ions, as in 1,1′-methylenebis(pyridinium) dication (MDP, 1 ), would appear to be intrinsically reactive and to be a reasonably strong carbon acid, as ionization would produce the ylide 2 (Scheme ). MDP is surprisingly easy to make from the reaction of pyridine with an excess of methylene chloride .…”

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Unusual Stability and Carbon Acidity of a Dicationic Carbon Species

2013

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1,1'-Methylenebis(pyridinium) dication (MDP) is an unusual ion with two formal positively charged substituents attached to a central carbon, yet it is remarkably stable to hydrolysis at pH < 8. However, above this pH it undergoes a biphasic reaction liberating two equiv of pyridine sequentially. The rate of the first phase is second order in hydroxide ion, while that of the second is pH-independent. The first phase is also accompanied by the generation of a chromophore at 366 nm, which has been identified as a pyridine-ring-opened unsaturated iminoaldehyde formed by an ANRORC-type mechanism. This intermediate then undergoes ring closure to give the second equiv of pyridine and formaldehyde. Below pD 8 there is a very slow alternative pathway for degradation that is first order in hydroxide ion, liberates only one equiv of pyridine, and forms N-(hydroxymethyl)pyridinium ion. Deuterium exchange of the central methylene in D2O is faster than the breakdown of MDP and is predominantly OD(-)-catalyzed with a small amount of buffer catalysis. The estimated pKa of MDP dication in H2O, 21.2 at 25 °C and I = 1.0 M (KCl), is unexpectedly high but is about 9 units lower than that for the monocationic N-methylpyridinium ion. Deuterium exchange also occurs at the 2 and 6 positions of the pyridinium rings, but at a lower rate that is first order in deuteroxide ion and competitive with the breakdown of MDP only below pD 11.

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A Novel Preparation of the 1,3-Benzoxazepine Ring System

Cited by 7 publications

References 0 publications

Reaction of Dichloromethane with Pyridine Derivatives under Ambient Conditions

Reaction of Dichloromethane with Pyridine Derivatives under Ambient Conditions

Interrupted Nef and Meyer Reactions: A Growing Point for Diversity-Oriented Synthesis Based on Nitro Compounds

Unusual Stability and Carbon Acidity of a Dicationic Carbon Species

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