A re-investigation of the Fries rearrangement of 3-chlorophenyl acetate and synthesis of 2-azido-1-(4-(benzyloxy)-2-chlorophenyl)ethanone from 4-bromo-3-chlorophenol

The Fries rearrangement of 3-chlorophenyl acetate provided the expected 4-chloro-2-hydroxy-acetophenone as the major product and 2,4-diacetyl resorcinol and 2-chloro-4-hydroxy-acetophenone as minor products. 4-Benzyloxy-2-chloroacetophenone was prepared by a Heck reaction and then elaborated to 4-benzyloxy-2-chlorophenacyl azide.     

A Mild and Regioselective Route to Functionalized Quinazolines

A Rh‐catalyzed ortho‐amidation cyclocondensation sequence gave a range of 4‐aminoquinazolines in high yield. The method features a remarkably mild C(sp²)?H activation step and can be exploited to rapidly access compounds with established biological activity.     

Preparation of Pseudo-Arsonolipids: Dl-2,3-Diacyloxybutane-1,4-Bis(Arsonic Acids)

Abstract

The title pseudo-arsonolipid with palmitoyl side chain has been prepared in ～70% yield from its parent DL-2,3-dihydroxybutane-1,4-bis(arsonic acid) after reduction of the As(V) to As(III) by thiophenol, acylation with palmitoyl chloride in the presence of pyridine and catalytic amounts of 4-(dimethylamino)pyridine, and reoxidation of As(III) to As(V) by hydrogen peroxide. In CDCl₃/CD₃OD esterification of the –AsO₃H₂ groups was detected by ¹H NMR.     

Short and Efficient Syntheses of Protoberberine Alkaloids using Palladium‐Catalyzed Enolate Arylation

A concise synthesis of the biologically active alkaloid berberine is reported, and a versatile palladium‐catalyzed enolate arylation is used to form the isoquinoline core. The overall yield of 50 % is a large improvement over the single, previous synthesis. By design, this modular route allows the rapid synthesis of other members of the protoberberine family (e.g., pseudocoptisine and palmatine) by substitution of the readily available aryl bromide and ketone coupling partners. Moreover, by combining enolate arylation with in situ functionalization, substituents can be rapidly and regioselectively introduced at the alkaloid C13 position, as demonstrated by the total synthesis of dehydrocorydaline. The avoidance of electrophilic aromatic substitution reactions to make the isoquinoline allows direct access to analogues possessing more varied electronic properties, such as the fluorine‐containing derivative synthesized here.     

On pseudospectra of matrix polynomials and their boundaries

In the first part of this paper (Sections 2-4), the main concern is with the boundary of the pseudospectrum of a matrix polynomial and, particularly, with smoothness properties of the boundary. In the second part (Sections 5-6), results are obtained concerning the number of connected components of pseudospectra, as well as results concerning matrix polynomials with multiple eigenvalues, or the proximity to such polynomials.

     

A metathesis-based approach to the synthesis of 2-pyridones and pyridines

The ring-closing metathesis reaction has been successfully employed to form a range of dihydropyridone intermediates, which are in the correct oxidation state to undergo a base-induced elimination to reveal the aromatic 2-pyridone. This mild and novel approach to six-membered heteroaromatic compounds then provides access to a wide variety of substituted pyridines in excellent overall yield.     

Coordination Complexes of a Neutral 1,2,4‐Benzotriazinyl Radical Ligand: Synthesis,Molecular and Electronic Structures,and Magnetic Properties

A series of d‐block metal complexes of the recently reported coordinating neutral radical ligand 1‐phenyl‐3‐(pyrid‐2‐yl)‐1,4‐dihydro‐1,2,4‐benzotriazin‐4‐yl ( 1 ) was synthesized. The investigated systems contain the benzotriazinyl radical 1 coordinated to a divalent metal cation, Mn^II, Fe^II, Co^II, or Ni^II, with 1,1,1,5,5,5‐hexafluoroacetylacetonato (hfac) as the auxiliary ligand of choice. The synthesized complexes were fully characterized by single‐crystal X‐ray diffraction, magnetic susceptibility measurements, and electronic structure calculations. The complexes [Mn( 1 )(hfac)₂] and [Fe( 1 )(hfac)₂] displayed antiferromagnetic coupling between the unpaired electrons of the ligand and the metal cation, whereas the interaction was found to be ferromagnetic in the analogous Ni^II complex [Ni( 1 )(hfac)₂]. The magnetic properties of the complex [Co( 1 )(hfac)₂] were difficult to interpret owing to significant spin–orbit coupling inherent to octahedral high‐spin Co^II metal ion. As a whole, the reported data clearly demonstrated the favorable coordinating properties of the radical 1 , which, together with its stability and structural tunability, make it an excellent new building block for establishing more complex metal–radical architectures with interesting magnetic properties.