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Exploring benzylic gem-C(sp³)-boron-silicon and boron-tin centers as a synthetic platform.

ABSTRACT: A stepwise build-up of multi-substituted C_sp³ carbon centers is an attractive, conceptually simple, but often synthetically challenging type of disconnection. To this end, this report describes how gem-α,α-dimetalloid-substituted benzylic reagents bearing boron/silicon or boron/tin substituent sets are an excellent stepping stone towards diverse substitution patterns. These gem-dimetalloids were readily accessed, either by known carbenoid insertion into C-B bonds or by the newly developed scalable deprotonation/metallation approach. Highly chemoselective transformations of either the C-Si (or C-Sn) or the C-B bonds in the newly formed gem-C_sp³ centers have been achieved through a set of approaches, with a particular focus on exploiting the synthetically versatile polarity reversal in organometalloids by λ³-aryliodanes. Of particular note is the metal-free arylation of the C-Si (or C-Sn) bonds in such gem-dimetalloids via the iodane-guided C-H coupling approach. DFT calculations show that this transfer of the (α-Bpin)benzyl group proceeds via unusual [5,5]-sigmatropic rearrangement and is driven by the high-energy iodine(iii) center. As a complementary tool, the gem-dimetalloid C-B bond is shown to undergo a potent and chemoselective Suzuki-Miyaura arylation with diverse Ar-Cl, thanks to the development of the reactive gem-α,α-silyl/BF₃K building blocks.

SUBMITTER: Chen WW

PROVIDER: S-EPMC8356736 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Silicon and boron share many similarities, both chemically and biochemically, including having similar effects on bone, although their mechanisms of action are not known. Here we compared the loading of silicon and boron into bone, their localization and how they are influenced by age (growth & development), to obtain further clues as to the biological effects of these elements and, especially, to see if they behave the same or not. Bone samples were obtained from two different studies where female Sprague Dawley rats had been maintained on a normal maintenance diet for up to 43 weeks. Total bone elemental levels were determined by ICP-OES following microwave assisted acid digestion. Silicon and boron levels in the decalcified bones (i.e. the collagen fraction) were also investigated. Silicon and boron showed marked differences in loading and in their localization in bone. Highest silicon and lowest boron concentrations were found in the under-mineralized bone of younger rats and lowest silicon and highest boron concentrations were found in the fully mineralized bone of the adult rat. Overall, however total bone silicon content increased with age, as did boron content, the latter mirroring the increase in calcium (mineral) content of bone. However, whereas silicon showed equal distribution in the collagen and mineral fractions of bone, boron was exclusively localized in the mineral fraction. These findings confirm the reported association between silicon and collagen, especially at the early stages of bone mineralization, and show that boron is associated with the bone mineral but not connective tissues. These data suggest that silicon and boron have different biological roles and that one is unlikely, therefore, to substitute for the other, or at least boron would not substitute for Si in the connective tissues. Finally, we noted that silicon levels in the mineral fraction varied greatly between the two studies, suggesting that one or more nutritional factor(s) may influence the loading of Si into the mineral fraction of bone. This and the nature of the interaction between Si and collagen deserve further attention.

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Exploring benzylic gem-C(sp³)-boron-silicon and boron-tin centers as a synthetic platform.

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Exploring benzylic gem-C(sp3)-boron-silicon and boron-tin centers as a synthetic platform.

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OmicsDI is part of the ELIXIR infrastructure

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Exploring benzylic gem-C(sp³)-boron-silicon and boron-tin centers as a synthetic platform.