The impact of Novel Process Windows on the Claisen rearrangement

Kobayashi, Hiroki; Driessen, Brian; Osch, Dannie J. G. P. van; Talla, A Ali; Noël, Timothy; Hessel, Volker

doi:10.1016/j.tet.2013.02.038

Cited by 31 publications

(51 citation statements)

References 47 publications

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“…Despite the solvent, they vary considerably with increasing temperature leading to the advantage of obtaining the allyl phenol as the desired product. Indeed, at high temperatures in flow, there is much profitable situation compared to the batch study [82], and hardly any furan cyclization or other follow-up product was found [64]. This is probably partly due to the strong reduction in residence time which allows (partly) cutting off the follow-up products formation which emerge on a later time scale than the desired (intermediate) product.…”

Section: Impact Factors Transiɵon Statesmentioning

confidence: 94%

“…In the last decade, microreactor technology was much further developed and even applied on industrial scale [63], including the Claisen rearrangement [64][65][66][67]. It became almost a routine part of chemical reactor engineering.…”

Section: Beyond the Batch Process -Improvement Opportunities Through mentioning

confidence: 99%

“…A particular important point is that solvent selection for high temperature windows is not restricted anymore by the solvent's boiling point and low-boiling solvents can be used at the desired high temperature [64]. Following these lines, the Claisen rearrangement of APE to ortho-allyl phenol (o-AP) was performed in subcritical water (SCW) [65,85].…”

Section: Solvent Effects (Including Reaction Environment)mentioning

confidence: 99%

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The Claisen Rearrangement – Part 2: Impact Factor Analysis of the Claisen Rearrangement, in Batch and in Flow

et al. 2014

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In Part 2, the factors impacting the Claisen rearrangement both in batch and flow processing are analyzed, including the choice of substituent, catalyst, temperature, pressure, concentration, flow rates, and solvent. Part 1 of this review series discussed the potential of using short‐time spectroscopy and quantum mechanical calculations to elucidate the mechanism and transition state of the Claisen rearrangement. Flow processing offers profound opportunities for studying these factors known to impact the Claisen rearrangement done in batch. It is shown that the same impact factors also rule flow processing, yet now superposed by the very different residence and reaction time settings and by novel process windows which go beyond conventional processing. As a result, massive intensification can be reached and a mechanistic analysis can be done in entirely unpaved processing fields. This links to the analysis given in part 1: it is likely that flow processing can further promote the understanding of the mechanism and transition state of the Claisen rearrangement and, thereby, promote the achievement of better reaction performance.

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Section: Impact Factors Transiɵon Statesmentioning

confidence: 94%

Section: Beyond the Batch Process -Improvement Opportunities Through mentioning

confidence: 99%

Section: Solvent Effects (Including Reaction Environment)mentioning

confidence: 99%

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The Claisen Rearrangement – Part 2: Impact Factor Analysis of the Claisen Rearrangement, in Batch and in Flow

et al. 2014

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“…The fast heat transfer even allows to carry out reactions in the absence of any solvent, highlighting the green aspect of continuous-flow processing in microreactors. [91][92][93] An even faster heat transfer can be achieved by using microwave 94 or induction heaters. 95 Microwave heating is enabled by absorbance of the energy due to interaction of dipoles with the microwaves.…”

Section: Heat Transport Phenomenamentioning

confidence: 99%

Beyond Organometallic Flow Chemistry: The Principles Behind the Use of Continuous-Flow Reactors for Synthesis

Noël

Hessel

2015

Topics in Organometallic Chemistry

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Flow chemistry is typically used to enable challenging reactions which are difficult to carry out in conventional batch equipment. Consequently, the use of continuous-flow reactors for applications in organometallic and organic chemistry has witnessed a spectacular increase in interest from the chemistry community in the last decade. However, flow chemistry is more than just pumping reagents through a capillary and the engineering behind the observed phenomena can help to exploit the technology's full potential. Here, we give an overview of the most important engineering aspects associated with flow chemistry. This includes a discussion of mass-, heat-, and photon-transport phenomena which are relevant to carry out chemical reactions in a microreactor. Next, determination of intrinsic kinetics, automation of chemical processes, solids handling and multistep reaction sequences in flow are discussed. Safety is one of the main drivers to implement continuous-flow microreactor technology in an existing process and a brief overview is given here as well. Finally, the scale-up potential of microreactor technology is reviewed.

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“…Microreactor technology has also been proven beneficial for the Claisen rearrangement [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Photo-Claisen Rearrangement of Allyl Phenyl Ether in Microflow: Influence of Phenyl Core Substituents and Vision on Orthogonality

2016

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We converted diverse commercial meta-substituted phenols to the allyl-substituted precursors via nucleophilic substitution using batch technology to allow processing these in microflow by means of the photo-Claisen rearrangement. The latter process is researched on its own, as detailed below, and also prepares the ground for a fully continuous two-step microflow synthesis, as outlined above. It is known that batch processing of electronically deactivated phenols (e.g., bearing a cyano or nitro group) has several orders of magnitude lower reactivity than their parental counterparts [1]. Thus, we here explore if the high quantum yield of microflow, yet at very short residence time, is sufficient to activate the deactivated molecules. In addition, the realization of a true orthogonal two-step flow synthesis can open the door to a large synthetic scope of our approach and possibly overcome limitations due to missing orthogonality of our previously reported thermal approach of combined nucleophilic substitution-Claisen rearrangement in microflow. Consequently, we make for our photo microflow approach an orthogonality check, as previously reported for the thermal approach, and compare both. To get a broader picture, we have investigated some major parametric sensitivities such as the irradiation intensity, the choice of solvent, the reactant concentration, and, most notably, the influence of the substitution pattern. The irradiation intensity was varied by increasing distance between a lamp and the microflow capillary. In addition, the normal photoClaisen microflow process (at room temperature) is compared to a high-temperature photo-Claisen microflow process, to check the potential of such novel process window [2]. This is difficult to realize in batch, as the combination of strong ultraviolet (UV) irradiation and high temperature causes a high hazard potential. Yet, under microflow, this can be safely handled.

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The impact of Novel Process Windows on the Claisen rearrangement

Cited by 31 publications

References 47 publications

The Claisen Rearrangement – Part 2: Impact Factor Analysis of the Claisen Rearrangement, in Batch and in Flow

The Claisen Rearrangement – Part 2: Impact Factor Analysis of the Claisen Rearrangement, in Batch and in Flow

Beyond Organometallic Flow Chemistry: The Principles Behind the Use of Continuous-Flow Reactors for Synthesis

Photo-Claisen Rearrangement of Allyl Phenyl Ether in Microflow: Influence of Phenyl Core Substituents and Vision on Orthogonality

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