Electron Exchange Polymers. X. A General Method for the Preparation of Phenolic Polystyrenes<sup>1a</sup>

Stern, Robert; English, James P.; Cassidy, Harold G.

doi:10.1021/ja01578a055

Cited by 33 publications

(2 citation statements)

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“…The rest had to be prepared starting from phenol 6 . The conversion of alkylphenols 8 to methoxymethoxybenzaldehydes 11 was achieved in two ways: (i) by introducing the aldehyde group at the 2-position to form 9 and subsequently 11 or (ii) by formation of 4-alkylmethoxymethoxy phenyl ether ( 10 ), ortho metalation, and subsequent reaction with dimethylformamide . Better yields resulted from the second way.…”

Section: Resultsmentioning

confidence: 99%

Selectivity in the Photodimerization of 6-Alkylcoumarins

et al. 2003

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Coumarin and 6-alkylcoumarins (alkyl = C(1) to C(16)) were photodimerized in homogeneous solvents differing in polarity and in aqueous micellar solutions. The four possible photodimers, syn head-to-head (hh), anti head-to-head, syn head-to-tail (ht), and anti head-to-tail, were identified through a combination of X-ray analysis and NMR spectroscopy. In 6-methylcoumarin the concentration-corrected dimerization (quantum) yield increases with decreasing concentration of the educt; anti-hh was formed exclusively in nonpolar solvents and upon triplet sensitization and was the main product under all conditions except for ionic micellar systems, which direct to preferred syn-hh dimerization. Long alkyl substituents, however, lead to anti-hh in polar solvents and in micelles, too. Predominating ht dimer formation was observed for nonsubstituted coumarin in polar solvents only. Thus, syn/anti and hh/ht selectivity can be steered by varying the 6-alkyl substituent. Syn-hh photodimers of 6-methylcoumarin can be photochemically split into the monomers; they partly proved thermally unstable against acids, bases, methanol, and on SiO(2) surfaces.

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Section: Resultsmentioning

confidence: 99%

Selectivity in the Photodimerization of 6-Alkylcoumarins

et al. 2003

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“…Analytical data were in accordance with those previously published. [38] However, no NMR assignments were given. 1 C-3, C-3Ј), 122.6 (C-2, C-2Ј), 147.3 (C-1, C-1Ј) ppm.…”

Section: Synthesis Of Catechol Derivativesmentioning

confidence: 99%

Synthesis of Bis(catechol) Ligands Derived from Tröger's Base and Their Dinuclear Triple‐Stranded Complexes with Titanium(IV) Ions

Kiehne¹,

Lützen²

2007

Eur J Org Chem

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Bis(catechol) ligands derived from 2,8-disubstituted analogues of Tröger's base and monofunctionalized MOMprotected or unprotected catechols bearing both rigid and flexible spacers were synthesized, which gave rise to dissymmetric oxygen donor ligands whose geometry is defined by the V-shaped and rigid structure of the core of Tröger's base. These racemic ligands undergo self-assembly to dinuclear

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Heteroatom‐Facilitated Lithiations

Gschwend¹,

Rodriguez²

1979

Organic Reactions

185

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Some 25 years have elapsed since the topic of metalation reactions was reviewed by Gilman and Morton. The intervening years have been notable for intensive explorations in this area, in part because many organolithium reagents are now commercially available. Specifically, research efforts have been characterized by the discovery of new functional groups that promote metalation, elaboration of novel heterocyclic and olefinic substrates as metalatable species, recognition of new types of lithiating agents, and the continuation of efforts to define accurately the mechanism of metalation. Accordingly, heteroatom‐facilitated lithiation has become recognized as an increasingly important tool, not only in the elaboration of carbocyclic aromatic and heteroaromatic systems, but also in synthetic aliphatic chemistry. A few recent reviews have covered the topic in a more limited or less specific sense. It is the purpose of this chapter to survey and classify the vast accumulation of heteroatom‐facilitated lithiations recorded since the first coverage in Organic Reactions . As outlined by Gilman and Morton, the terms “metalation” in general and “lithiation” in particular denote any replacement of a hydrogen atom by metal or lithium. In this review, however, lithiation is defined as the exchange of a hydrogen atom attached to an sp 2 ‐hybridized carbon atom by lithium to form a covalent lithium‐carbon bond. More specifically, discussion is limited to those metalations that, through the influence of a heteroatom, are characterized by rate enhancement and regioselectivity. In fact, lithiation reactions of this type are noted for an extraordinarily high degree of regioselectivity, metalation generally occurring on the sp 2 ‐carbon atom closest to the heteroatom. Based on the relative position of the heteroatom, such lithiations are conveniently classified into two principal categories: alpha and beta ( ortho ) lithiations. In alpha lithiations the metalating agent deprotonates the sp 2 ‐carbon atom alpha to the heteroatom to form a carbonlithium bond. This sp 2 ‐carbon atom may be part of an olefinic or heteroaromatic π system. In beta lithiations the metalating agent is directed to deprotonate the sp 2 ‐carbon atom beta to the heteroatom‐containing substituent. The sp 2 ‐carbon atom can be part of an aromatic or an olefinic π system. It should be noted that the designation “ ortho metalation” is used specifically for the beta metalation of carbocyclic aromatic systems. This chapter surveys all systems in which alpha and beta lithiations have been observed, with the exception of ferrocenes.

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Electron Exchange Polymers. X. A General Method for the Preparation of Phenolic Polystyrenes^1a

Cited by 33 publications

References 1 publication

Selectivity in the Photodimerization of 6-Alkylcoumarins

Selectivity in the Photodimerization of 6-Alkylcoumarins

Synthesis of Bis(catechol) Ligands Derived from Tröger's Base and Their Dinuclear Triple‐Stranded Complexes with Titanium(IV) Ions

Heteroatom‐Facilitated Lithiations

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Electron Exchange Polymers. X. A General Method for the Preparation of Phenolic Polystyrenes1a

Cited by 33 publications

References 1 publication

Selectivity in the Photodimerization of 6-Alkylcoumarins

Selectivity in the Photodimerization of 6-Alkylcoumarins

Synthesis of Bis(catechol) Ligands Derived from Tröger's Base and Their Dinuclear Triple‐Stranded Complexes with Titanium(IV) Ions

Heteroatom‐Facilitated Lithiations

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Electron Exchange Polymers. X. A General Method for the Preparation of Phenolic Polystyrenes^1a