The direct production of tri- and hexa-substituted benzenes from ketones under mild conditions

Elmorsy, Saad S.; Pelter, Andrew; Smith, Keith

doi:10.1016/s0040-4039(00)79896-0

Cited by 111 publications

(72 citation statements)

References 6 publications

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“…Treatment of 2Ј-bromoacetophenone with silicon tetrachloride at 0°C in ethanol [10] provided the desired tribrominated precursor 1 in excellent yield. It should be noted that Müllen et al report that silicon tetrachloride is ineffective for this reaction and for this reason they em-Scheme 2.…”

Section: Resultsmentioning

confidence: 99%

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives

et al. 2015

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Following a route described by Müllen et al. we improved the preparation of 1,2,3‐tris(3″‐iodobiphenyl‐2′‐yl)benzene (4). During the required iododesilylation with iodine monochloride the unexpected formation of a mono‐chlorinated compound 6 as major product was observed, when an excess of the iodination reagent was employed. The reaction mechanism for the formation of this compound involving an oxidizing process is discussed. X‐ray crystallography of the subsequent alkynylated product 7 proves the location of the chlorine atom at the central benzene ring. The related compound 5 was likewise investigated by X‐ray analysis revealing a preferred solid‐state conformation (“2‐up‐1‐down”) different from that of the chlorinated compound (“propeller” conformation). Compound 7 showed remarkable conformational dynamics in solution as observed by 1H NMR spectroscopy. Temperature‐dependent measurements allowed the calculation of an energy difference of two major conformers of ca. 2 kJ/mol and a rotational barrier ΔGrot of ca. 77 kJ/mol. These values were convincingly confirmed by DFT calculations. A subsequent Sonogashira reaction of 4 with a suitable bipyridine derivative provided a unique trivalent bipyridine derivative.

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Section: Resultsmentioning

confidence: 99%

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives

et al. 2015

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“…20 This resulted dendrimer was then subjected to a series of divergent Suzuki couplings for functionalization of the final dendrimers with different groups. 21 The synthetic protocol is simple and could be easily modified to obtain either conjugated or saturated dendrimers bearing variable groups.…”

Section: 11mentioning

confidence: 99%

A New Efficient Convergent Synthesis of Conjugated Aryl-containing Dendrimers

El‐Deeb¹,

Lee²

2010

Bulletin of the Korean Chemical Society

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Dendrimers are branched macromolecules that consist of a core, one or more dendrons, and surface groups. Due to their controlled mass, uniform structure, surface functionality and good solubility (relative to linear polymers), they have been studied for a wide range of pharmaceutical applications including solubility enhancement, 1,2 drug delivery, 3,4 MRI contrast agents, 5,6 neutron capture therapy, 7 gene therapy 8 and photodynamic therapy. 9 At the same time, conjugated dendrimers have recently attracted special attention for their potential use in organic light emitting diodes, either as light emitting or chargetransporting layers. 10,11The unique structure of dendrimers allowed for better and more flexible control of their properties. The fact that different parts of dendrimer structure can have different functions allows for independent optimization of the electronic and processing properties. For example, the core in dendrimer can be selected to give the desired luminescence color, while the surface groups could be controlled to give the desired solubility. 10 Despite the large amount of research focused at dendrimers and the large number of prospects for their potential uses, very few dendrimer-based products have reached an industrial development stage. Among the reasons for the slow progress in this area are the multi-step synthetic routes commonly employed for the synthesis of dendrimers and the purification processes required to remove the excess of reagents and byproducts at each generation build-up. Accordingly, much effort have been devoted to develop synthetic methodologies that either follow a growing pattern from a multivalent core in an interactive sequence (divergent), or a dendron is grafted on to the core (convergent). Some progress has been made in this regard, including the polyamidoamine (PAMAM) dendrimers reported by Tomalia, 12 phosphorus-containing dendrimers by Majoral and co-workers, 13 aliphatic polyester dendrimers by Fréchet and co-workers, 14 and the 3,5-dihydroxybenzyl alcohol based dendrimers by Bourrier and Kakkar. 15 A number of click chemistry protocols have been also applied recently for the preparation of dendrimers, employing Diels-Alder reaction, 16 thiol-ene reactions 17 and azide-alkyne reactions.18,19 However, there are still needs to make these processes viable for industrial scale applications.Herein we describe a new convergent synthesis of conjugated dendrimers starting with acetyl substituted dendrons which were dehydrated under the effect of tetrachlorosilane to form a 1,3,5-trisubstituted phenyl core carrying three branches (dendrons) in a star shaped dendrimer. 20 This resulted dendrimer was then subjected to a series of divergent Suzuki couplings for functionalization of the final dendrimers with different groups. 21The synthetic protocol is simple and could be easily modified to obtain either conjugated or saturated dendrimers bearing variable groups. The products obtained in each preparation step are easily purified by simple crystallization, making the p...

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“…Table 1 provides some additional representative examples [6,10,[21][22][23][24][25][26][27][28][29].…”

Section: Other Examplesmentioning

confidence: 99%

The Synthesis of Tris‐Annulated Benzenes by Aldol Trimerization of Cyclic Ketones

Boorum¹,

Scott²

2002

Modern Arene Chemistry

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For the synthesis of tris-annulated benzene rings, the aldol trimerization of cyclic ketones has been known as a powerful tool since the 19 th century. Why the reaction works so well with some ketones (e.g., indanone) but fails so miserably with others (e.g., tetralone), however, has never been adequately explained. This chapter outlines the development and scrutiny of a hypothesis that says: formation of an a,b-unsaturated (conjugated) dimer from a cyclic ketone is vital to the success of an aldol trimerization reaction for the synthesis of a tris-annulated benzene; the reaction will fail with ketones that form only b,g-unsaturated (unconjugated) dimers. This hypothesis unifies much experimental chemistry and is supported by theoretical calculations.

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The direct production of tri- and hexa-substituted benzenes from ketones under mild conditions

Cited by 111 publications

References 6 publications

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives

A New Efficient Convergent Synthesis of Conjugated Aryl-containing Dendrimers

The Synthesis of Tris‐Annulated Benzenes by Aldol Trimerization of Cyclic Ketones

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The direct production of tri- and hexa-substituted benzenes from ketones under mild conditions

Cited by 111 publications

References 6 publications

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbi­phen­yl‐2′‐yl)benzene Derivatives

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbi­phen­yl‐2′‐yl)benzene Derivatives

A New Efficient Convergent Synthesis of Conjugated Aryl-containing Dendrimers

The Synthesis of Tris‐Annulated Benzenes by Aldol Trimerization of Cyclic Ketones

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Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives

Syntheses, Structures and Conformational Dynamics of 1,3,5‐Tris(3″‐ethynylbiphenyl‐2′‐yl)benzene Derivatives