A Practical Approach to Synthesize the C(9) –C(24) Fragment of (+)‐Discodermolide

Abstract

A practical and stereoselective synthesis of the C(9)-C(24) subunit of (＋)-discodermolide has been achieved. The strategy featured the construction of the key intermediate Z-trisubstituted vinyl iodide 12 from the dibromoolefin 6 via an efficient modified Tanino-Miyashita's approach. The union of the two fragments was carried out through a Suzuki cross-coupling reaction.

Shape‐directed platinum nanoparticle synthesis: nanoscale design of novel catalysts

“…Such a ratio results in overgrowth conditions where metal cations are reduced to zero-valent metal atoms at the corners and edges of the nanocrystal, forming branched and dendritic structures. [50,75] Growth occurs through a diffusion-limited process where the platinum precursor surrounding the particle is depleted as the particle grows, resulting in a concentration gradient directly around the growing particle. Protrusive particle features such as edges and corners are exposed to a higher precursor concentration and therefore have more favorable growth conditions than faces.…”

“…Protrusive particle features such as edges and corners are exposed to a higher precursor concentration and therefore have more favorable growth conditions than faces. [50,68,138] The overgrowth morphology caused by this concentration gradient is represented in Fig. 3.…”

“…This process is still commonly used industrially due to its ease of scalability; however, the resulting nanoparticles suffer from a lack of size monodispersity since the method has limited parameters for directing shape. [44,46,48] Electrochemical reduction is also common due to the exact control of the reduction potential and current waveform, both of which can direct shape and size, [49,50] as well as the ease of deposition directly onto a support of choice. [3,27,29] However, scalability via electrochemical reduction remains a challenge.…”

“…A general mechanism for the control of size and shape of the nanoparticles has not been established, but it is generally accepted that kinetics is the primary driving force. Control of reaction conditions causes a change in kinetics, thereby altering the rate of reduction [50,[68][69][70] or the growth along a specific facet. [71][72][73] Controllable reaction conditions include the addition of organic or inorganic ligands which bind to the surfaces of the growing nanoparticles and direct the growth of specific shapes by altering nucleation or growth kinetics.…”

“…The primary advantage of this method is that there is a high degree of size monodispersity for the nanocrystals and many parameters, such as the addition of foreign ions, can be altered to control the size and shape of the particles. [8,12,20,24,50,71,72,120,121] Wet Chemical Reduction/Colloidal Synthesis WCR has been reported to be very powerful for the synthesis of nanoscale metals because of its ability to produce narrow size distributions of shaped nanoparticles that are reproducible at larger scales. [69,70,122] The kinetics and mechanisms of this method were elaborated in 1997 by Finke and coworkers, [122] as well as Bönnemann and co-workers.…”