Goldsmith approach

Goldsmith and Soria (6b) reported a novel approach to a synthesis of the cyclopentanoid ring system 25 based on the 1,3-dipolar cycloaddition of p-bromobenzenesulfonyl azides with the electron-rich 1,4-cyclohexadienol ether 22 and subsequent ring contraction at moderate temperature (Scheme 9.6) (6a). 

The collisional impulse can be obtained by using the impulse-momentum equations [Goldsmith, I960]. However, this stereomechanical approach does not yield the transient stresses, collisional forces, impact duration, or collisional deformation of the colliding objects. These quantities have to be obtained from the analysis of stresses and strains of the solids due to the impact, which is introduced later. 

Anderson and co-workers (5,6) first exploited a group 4 cyclization in route to the construction of two aromatic trichothecene model systems, one of which is depicted in Scheme 17. The group 4 approach is embodied in the base catalyzed cyclization of keto bromide (182) to the modified trichothecene skeleton (184). Cyclization could be envisaged to proceed through the hemiketal intermediate (183). Due to the possibility of C-2 epimerization both epimers of the keto bromide (182) can be converted to product. A similar base catalyzed cyclization was peformed by Goldsmith and co-workers (58) in their preparation of ketone (187). In this case, epimerization of the starting keto chloride (186) was impossible consequently, only one of the two epimers underwent ring closure. 

J. Goldsmith, H. Guo, S.N. Hunt, Mingjiang Tao, and S. Koehler. Drag on intruders in granular beds A boundary layer approach. Physical Review E, 88 030201, September 2013. 

Today, much jewelry is still made in traditional workshops around the world by expert goldsmiths using manual metalworking skills but utilizing modern hand tools with limited use of machines. This craft approach leads to inconsistent product quality, a relative lack of design innovation, and is labor intensive. It is limited by available craft skills and is a relatively inefficient and time-consuming production technique. 

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