Sequential Horner-Emmons

Floreancig completed the total synthesis of (+)-dactylohde via a sequential Peterson olefination and an intramolecular Hosomi-Sakurai-Prins cycli-zation of the acetal-linked substrate (Scheme 32). Macrocychzation was performed by Horner-Emmons olefination as Smith did (Sect. 3.2.1). The key element of 2,6-cfs-tetrahydropyran in 155 was constructed via the sequential cyclization starting from acetal 156, which involved aldehyde 157 and 1,3-diol 158, synthesized via Denmark s asymmetric aldol reaction and Stille coupling. 

Within the context of total synthesis, the application of CM to a one-pot sequential protocol has the potential to dramatically simplify the preparation of complex natural products. Trost and co-workers recently demonstrated an elegant example of this, wherein a one-pot CM-Takai olefination reaction was used for the preparation of the antitumor agent callipeltoside A and various analogs (Scheme 21). By using a three-step, two-pot sequence employing this protocol, the synthetic route toward these compounds was shortened by five steps and olefin stereoselectivity was increased (4 1 to >8 1 E/Z) relative to previous syntheses employing a classical Emmons-Wadsworth-Horner approach. 

Kellogg, R. M. Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions. Chemtracts 2002, 15, 69-73. 

TMG (1) is used as a base in Horner-Wadsworth-Emmons (HWE) reactions [81]. For example, the sequential reaction of 1,3-diformylbenzene with different phosphorylglycines... 

The one-pot, organocatalytic Hayashi sequential reaction (HSR) of p-nitroacrylate (806), aldehyde (807), toluenethiol (808), and vinylphosphonate (805) allowed the synthesis of highly functionaKsed cyclohexanes (809) with very high enantioselectivity (up to 99 % ee). The one-pot synthesis consisted of the tertiary amine modified diarylprolinol silyl ether (810)-mediated asymmetric Michael reaction, a domino Michael reaction/the Horner-Wadsworth Emmons reaction, and a sulfa-Michael reaction (Scheme 205). ... 

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