Baylis-Hillman acetates synthesis

Moreover, a twofold SN -type domino reaction was reported by Krische and coworkers for the synthesis of y-butenolides 2-229 (Scheme 2.53) [128]. Treatment of Morita-Baylis-Hillman acetates 2-226 with trimethylsilyloxyfuran (2-227) in the presence of triphenylphosphane in THF at 0 °C led to 2-229 in yields of up to 94% and diastereoselectivities of >95 5. 

This reaction has been further extended to a catalytic procedure for the synthesis of allyl aryl sulfone derivativesl47 from Baylis-Hillman acetates 145 and sulfonyl hydrazides 146 using BU4NI as the catalyst and TBHP as an oxidation agent in water (Scheme 4.74) [116],... 

A twofold Sjj type domino organocatalytic reaction for the synthesis of y-butenolides 28 has been reported by Krische and coworkers [19], by treatment of Morita- Baylis- Hillman acetates 26 with trimethylsilyloxyfuran (27) in the presence of triphenylphosphine to afford 28 in yields up to 94% and diastereoselectivities of >95 5 dr (Scheme 4.6). 

Scheme 4.19 Baylis-Hillman acetates 30 in the synthesis of a-alkylidene-S-lactones 75.

Yadav et al made use of InBr3 to catalyze the Sn 2 reaction of Baylis-Hillman acetates with indoles for the synthesis of substituted indoles [161]. The authors had also reported that InBr3 was superior to In(OTf)3, Bi(OTf)3, Sc(OTf)3 or Yb(OTf)3 (Figure 8.70). 

A new route to 6-substituted pyrrolo[2,l-b]thiazoles 58 takes advantage of an intramolecular thermal cyclization of acetates 56 <07S3037>. These acetates are easily derived from the Morita-Baylis-Hillman adducts of thiazole-2-carboxaldehyde. This strategy has also been extended to the synthesis of the tricyclic analogs 60. 

Allylic substitution. Alkyltitanocenes are nucleophilic toward allyUc acetates such as those derived from Baylis-Hillman adducts. Accordingly, it is applicable to the synthesis of a-alkyl-a,p-unsaturated esters. 

Recently, organocatalytic enantioselective transformations of the densely functionalized Baylis-Hillman adducts and their derivatives have gained continuous interest, which opened a new access to the synthesis of optically active functionalized structures [125]. BH adducts and their derivatives include BH alcohols, BH acetates, BH carbonates, and halides, among which BH carbonates are more reactive and hence have received much attention recently. In this section, we will review all the reactions that appeared in the last few years with the use of BH carbonates as substrates. 

Synthesis of a series of novel functionalized achiral and chiral allyl boronates has been recently reported by Ramachandran via nucleophilic SNj -type addition of copper boronate species (generated from the boronates 37, 141, 142 under Miyaura conditions) [115,116] to various functionalized allyl acetates that tvere prepared either via vinylalumination or by Baylis-Hillman reaction with various aldehydes [117]. The resulting allylic boronates bearing an ester moiety (X=OR) were subsequently used for the synthesis of a-alkylidene-/3-substituted-y-butyrolactones by allylboration of aldehydes (Scheme 3.76). 

---