**3.** *In situ* **alcohol oxidation—Wittig/HWE reactions; other** *in situ* **aldehyde preparations run with subsequent Wittig/HWE sequences in one pot**

The tolerance of stabilized phosphoranes towards mild oxidants allows for the oxidation of an alcohol to an aldehyde and its Wittig reaction in one-pot (**Schemes 5** and **6**). As oxidants, activated MnO2 [43–46], barium permanganate [47, 48], tetra-*n*-propylammonium perruthenate (TPAP)/*N*-methylmorpholine *N*-oxide (NMO) [49–54] and TPAP/*N*,*N*,*N′*,*N′* tetramethylenediamine dioxide (TMEDAO2 ) [55], *o*-iodoxybenzoic acid (IBX) [56–58], Dess-Martin periodinane [59–61], DMSO-oxalyl chloride (Swern conditions) [62–64], DMSO-SO<sup>3</sup> -pyridine (Parikh-Doering oxidation) [38, 39] or DMSO-SO<sup>3</sup> -triethylamine [65], pyridinium chlorochromate (PCC) or PCC/celite [66–69] as well as pyridinium dichromate (PDC) [70] such as PDC encapsulated in sol gel [71] have been used. In addition, metal catalyzed aerobic oxidation reactions of aldehydes with concomitant olefination reactions are known, where [(eta*p*-cymene)RuCl2 ] 2 (**27**) [72], nanoparticulate ruthenium supported on highly porous aluminum oxyhydroxide [73] or on silica gel [74], and nickel nanoparticles [75, 76] (**Scheme 6**) have been used as catalyst in the case of a concomitant Wittig reaction and gold/palladium bimetallic nanoparticles in the case of a concomitant Horner-Wadsworth-Emmons (HWE) reaction [77], Cu(I)-phenanthroline as a catalyst in an oxidation: HWE: sequential procedure [78].

Taylor et al. give a good overview of the tandem oxidation-Wittig processes developed until 2005, focusing especially on the tandem oxidation process (TOP) developed by his group [43–46],

Wittig transformations of the aldehydes produced *in situ* allows for the manipulation of aldehydes that are inherently instable such as of silyl substituted aldehydes, propargyl aldehyde [97], and chiral γ-aminoaldehydes, the latter without loss of stereochemical integrity (**Scheme 5**) [89]. In the case of Wittig transformations of chiral α-aminoaldehydes, β-aminoalcohols were oxidized to α-aminoaldehydes with NaOCl in the presence of AcNH-TEMPO, where the crude α-aminoaldehydes gained from the oxidation were subjected directly to olefination to give

Tandem-, Domino- and One-Pot Reactions Involving Wittig- and Horner-Wadsworth-Emmons...

http://dx.doi.org/10.5772/intechopen.70364

9

Other preparation methods of aldehydes in conjunction with Wittig olefinations or HWE reactions have been reported. Thus, an oxidative cleavage of a glycol can be carried out in combination with a subsequent Wittig-olefination [102–105] (**Scheme 7**). Also a one-pot carboxylic acid to aldehyde reduction and Wittig reaction is known [106]. Finally, a Domino hydroformylation/Wittig olefination procedure has been developed, starting from allylamines (**Scheme 8**). The aldehyde is not isolated [107]. Domino/hydroformylation/Wittig olefination

protocols have been introduced with other olefinic starting materials, also [108–110].

Wittig products without loss of stereochemical integrity [99–101].

**Scheme 7.** Oxidative glycol cleavage—Wittig reaction.

**Scheme 8.** Hydroformylation—Wittig reaction.

**Scheme 6.** One-pot metal catalyzed oxidation of alcohols utilizing oxygen—Wittig reaction.

using activated MnO2 [79]. Over the years, this process has been used more often [40, 80–97] than the other processes shown above. Recently, also MnO2 derived molecular sieve material such as OMS-2 [KMn4+Mn3+O16*·*nH2 O] has been used with success in aerobic, catalytic one-pot oxidation Wittig reactions of benzylic and allylic alcohols to the respective cinnamates [98]. Overall, the Wittig transformations of the aldehydes produced *in situ* allows for the manipulation of aldehydes that are inherently instable such as of silyl substituted aldehydes, propargyl aldehyde [97], and chiral γ-aminoaldehydes, the latter without loss of stereochemical integrity (**Scheme 5**) [89]. In the case of Wittig transformations of chiral α-aminoaldehydes, β-aminoalcohols were oxidized to α-aminoaldehydes with NaOCl in the presence of AcNH-TEMPO, where the crude α-aminoaldehydes gained from the oxidation were subjected directly to olefination to give Wittig products without loss of stereochemical integrity [99–101].

Other preparation methods of aldehydes in conjunction with Wittig olefinations or HWE reactions have been reported. Thus, an oxidative cleavage of a glycol can be carried out in combination with a subsequent Wittig-olefination [102–105] (**Scheme 7**). Also a one-pot carboxylic acid to aldehyde reduction and Wittig reaction is known [106]. Finally, a Domino hydroformylation/Wittig olefination procedure has been developed, starting from allylamines (**Scheme 8**). The aldehyde is not isolated [107]. Domino/hydroformylation/Wittig olefination protocols have been introduced with other olefinic starting materials, also [108–110].

**Scheme 7.** Oxidative glycol cleavage—Wittig reaction.

**Scheme 8.** Hydroformylation—Wittig reaction.

using activated MnO2

**Scheme 5.** One-pot MnO2

8 Alkenes


OMS-2 [KMn4+Mn3+O16*·*nH2

the other processes shown above. Recently, also MnO2

**Scheme 6.** One-pot metal catalyzed oxidation of alcohols utilizing oxygen—Wittig reaction.

[79]. Over the years, this process has been used more often [40, 80–97] than

Wittig reactions of benzylic and allylic alcohols to the respective cinnamates [98]. Overall, the

O] has been used with success in aerobic, catalytic one-pot oxidation

derived molecular sieve material such as
