Kulinkovich

For a review of carbene methods for introducing formyl and acyl groups into organic molecules, see Kulinkovich, O.G. Russ. Chem. Rev., 1989, 58, 711. 

A myxobacterium Stigmatella aurantiaca uses stigmolone (22) as its fruiting body inducing pheromone. Both the enantiomers of 22 were synthesized by Mori [56] and also byEnders [57], and found to be equally bioactive. Scheme 33 shows Mori s synthesis, and Scheme 34 summarizes that of Enders. Since both (R)- and (S)-22 were bioactive, ( )-22 was synthesized in a very efficient manner by Kulinkovich (Scheme 35) [58]. 

The first synthetically useful reaction of titanium complexes of type 4, leading to the formation of two new carbon—carbon bonds, was developed by Kulinkovich et al. [55]. They found that treatment of a carboxylic acid ester with a mixture of one equivalent of titanium tetraisopropoxide and an excess of ethylmagnesium bromide at —78 to —40 °C affords 1-alkylcyclopropanols 9 in good to excellent yields (Scheme 11.2) [55,56], This efficient transformation can also be carried out with sub-stoichiometric amounts of Ti(OiPr)4 (5—10 mol%) [57,58]. In this case, an ethereal solution of two equivalents of EtMgBr is added at room temperature to a solution containing the ester and Ti(OiPr)4. Selected examples of this transformation are presented in Table 11.1 (for more examples, see ref. [26a]). 

The versatile Ti(II) chemistry available using preformed (alkene)Ti(OiPr)2 species was opened up by the discovery of the Kulinkovich cyclopropanation reaction [55]. Since 1995, Sato and collaborators have developed a wide range of elegant and synthetically useful reactions based on the Ti(OiPr)4/iPrMgCl reagent [56]. In particular, it was reported that the Ti(II) complex (q2-propene)Ti(OiPr)2, preformed from Ti(OiPr)4 and 2 equivalents of iPrMgCl, reacts with allylic compounds, such as halide, acetate, carbonate, phosphate, sulfonate, and aryl ether derivatives, to afford allyltitanium compounds as depicted in Scheme 13.27 [57]. 

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