Commodity chemical 2-methyl-1,3-propanediol is converted (two steps) into a 1:1 diastereomer mixture of 1'-(3'-bromo-2'-methylpropyl) 10-camphorsulfonates (casylates)(2S and 2R  ). Crystallization yields the higher-melting 2S  in >99.9:0.1dr. Four-step, silver-mediated configuration inversion of the mother liquor from the first crystallization (>65% 2R)   and repeat crystallization affords a >60% total yield. The 40% remaining material can be used in additional crystallization-inversion-crystallization sequences, and the silver and casylate moieties can be recycled, further increasing the total yield and atom economy. Manipulation of 3R  (made in two steps from highly pure 2S  ) affords a range of >99.9:0.1er building blocks (either R  or S ). Use of one such block will be shown in a greatly shortened synthesis of (-)-hemibourgeanic acid.

Silver-mediated, scalable, atom-economical route to a range of >99.9:0.1er difunctional C<sub>4</sub> secondary methyl synthons

246th National Meeting (2013)

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Silver-mediated, scalable, atom-economical route to a range of >99.9:0.1er difunctional C4 secondary methyl synthons

Silver-mediated, scalable, atom-economical route to a range of >99.9:0.1er difunctional C₄ secondary methyl synthons