Polypropionate synthesis

Scheme 24) [38]. Chemoselective enolization of the less substituted enone moiety under hydrogenation conditions accompanied by subsequent aldol reaction provided the corresponding hydroxyl-enones, such as 87-89, which could be converted to various building blocks for polypropionate synthesis. p-Me2N styryl vinyl enone also was employed successfully as an enolate precursor, as demonstrated by the formation of hydroxy enone 90. 

Silyltitanation of 1,3-dienes with Cp2Ti(SiMe2Ph) selectively affords 4-silylated r 3-allyl-titanocenes, which can further react with carbonyl compounds, C02, or a proton source [26]. Hydrotitanation of acyclic and cyclic 1,3-dienes functionalized at C-2 with a silyloxy group has been achieved [27]. The complexes formed undergo highly stereoselective addition with aldehydes to produce, after basic work-up, anti diastereomeric (3-hydroxy enol silanes. These compounds have proved to be versatile building blocks for stereocontrolled polypropionate synthesis. Thus, the combination of allyltitanation and Mukayiama aldol or tandem aldol-Tishchenko reactions provides a short access to five- or six-carbon polypropionate stereosequences (Scheme 13.15) [28],... 

Polypropionate synthesis, 20 138 Polypropylene (PP), 20 523-548 24 272. See also Olefin fibers Propylene polymer entries Spheripol technology Spherizone technology advanced material, 2 693 asbestos substitute, 3 314t, 315 can coatings, 26 39 catalyst systems for, 20 525-528 catalyst yield for, 20 531-532 coatings, 7 40 conducting, 7 525... 

SCHEME 10.3. Example of iterative sequences of aldol and crotylation reactions in planning of polypropionate synthesis. 

A different strategy that has also been well smdied for polypropionate synthesis is the hetero-Diels-Alder (HDA) reaction. The Danishefsky group has reported on one of the first attempts to obtain polypropionates via this method-ology. His group focused on the pyran subunit, a... 

SCHEME 10.45. Application of the Roush group s crotylboronates in polypropionate synthesis. 

SCHEME 10.46. Application of Leighton group s crotylsilanes in polypropionate synthesis. 

SCHEME 10.47. Application of crotyl titanium in polypropionate synthesis. 

SCHEME 10.49. Palladium-catalyzed generation of main group allenyl metals and their use in polypropionate synthesis. 

SCHEME 10.52. Naked sugar approach for polypropionate synthesis. 

Paterson I, Wallace DJ, Velazquez SM. Studies in polypropionate synthesis high -rr-face selectivity in syn and anti aldol reactions of chiral boron enolates of lactate-derived ketones. Tetrahedron Lett. 1994 35 9083-9086. 

Paterson I, Goodman JM, Isaka M. Aldol reactions in polypropionate synthesis high rr-face selectivity of enol hori-nates from a-chiral methyl and ethyl ketones under substrate control. Tetrahedron Lett. 1989 30 7121-7124. 

Paterson I, Tillyer RD. Studies in polypropionate synthesis high TT-face selectivity in syn aldol reactions of tin(II) enolates from (R)- and (S)-l-benzyloxy-2-methylpentan-3-one. Tetrahedron Lett. 1992 33 4233 236. 

Brazeau JF, Mochirian P, Prevost M, Guindon Y. Stereopentads derived from a sequence of Mukaiyama aldolization and free radical reduction on a-methyl-(3-alkoxy aldehydes a general strategy for efficient polypropionate synthesis. J. Org. Chem. 2009 74 64-74. 

Paterson I, Chen DYK, Acena JL, Franklin AS. Studies in marine polypropionate synthesis total synthesis of (—)-baconipyrone C. Org. Lett. 2000 2(11) 1513-1516. 

Paterson, I. and Perkins, M.V. (1992) Studies in polypropionate synthesis stereoselective synthesis of (—)-denticulatins A and B. Tetrahedron Lett., 33,801-804. 

Beye, G.E., Goodman, J.M., and Ward, D.E. (2009) Synthetic studies on siphonariid polypropionates Synthesis and isomerization of the caloimdrin B trioxaadamantane ring system. Org. Lett., 11, 1373-1376. 

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