MEYER - SCHUSTER Propargyl alcohol rearrangement

MEYER - SCHUSTER Propargyl alcohol rearrangement Add catalyzed rearrangement of acetylenic alcohols into o, -unsaturated carbonyl derivatives... 

The products from the acid-catalyzed hydration of a-tertiary alcohols 30 (Meyer-Schuster and Rupe rearrangements) are formed via the mesomeric propargyl-allenyl cation (equation 9) and have been extensively investigated28. 

When X=OH, this conversion of acetylenic alcohols to unsaturated aldehydes or ketones is called the Meyer-Schuster rearrangement The propargyl rearrangement can also go the other way that is, 1-haloalkenes, treated with organocopper compounds, give alkynes. ... 

It is noteworthy that the indenyl complex RuCl(ri -C9H7)(PPh3)2l4 provides an efficient catalyst precursor for the anti-Markovnikov hydration of terminal alkynes in aqueous media, especially in micellar solutions with either anionic (sodium dode-cylsulfate (SDS)) or cationic (hexadecyltrimethylammonium bromide (CTAB)) surfactants [38]. This system can be applied to the hydration of propargylic alcohols to selectively produce P-hydroxyaldehydes, whereas RuCl(Cp)(PMe3)2 gives a,P-unsat-urated aldehydes (the Meyer Schuster rearrangement products)(Scheme 10.8) [39]. 

Finally, the synthesis is completed by using the Meyer-Schuster rearrangement of the Aren-van Dorp synthesis on enone acetal 152. Treatment of 152 with lithium etoxyacetilide in THF gives an unstable tertiary allylic-propargylic alcohol that, when dissolved in methanol with a catalytic quantity of sulphuric acid produces 63 and its epimer 98 in a proportion of 7 3, respectively, in 42% yield. 

Keywords propargyl alcohol, TsOH, Meyer-Schuster rearrangement, cinnamic aldehyde... 

H. Stark and co-workers prepared novel histamine Hs-receptor antagonists with carbonyl-substituted 4-[(3-phenoxy)propyl]-1/-/-imidazole structures. The Meyer-Schuster rearrangement was used for the synthesis of one of the compounds. The p-hydroxybenzaldehyde derivative was reacted with ethynylmagnesium bromide to afford a secondary propargylic alcohol. Upon hydrolysis with 2N HCI in a refluxing ethanol/acetone mixture, the corresponding p-hydroxy cinnamaldehyde was obtained. 

Yoshimatsu, M., Naito, M., Kawahigashi, M., Shimizu, H., Kataoka, T. Meyer-Schuster Rearrangement of y-Sulfur-Substituted Propargyl Alcohols A Convenient Synthesis of a,P-Unsaturated Thioesters. J. Org. Chem. 1995, 60,4798-4802. 

Meyer-Schuster rearrangement. Ammonium vanadate, diphenylsilanedio), and an alkanedicarboxylic acid constitute an efficient catalytic system for the conversion of propargyl alcohols to a,/3-unsaturated aldehydes. 

Meyer-Schuster rearrangement. The conversion of propargylic alcohols to conjugated carbonyl compounds is effected by heating with MoOjfacac) and Bu2S=0 in o-dichlorobenzene at 100°. 

Representative procedure for the molybdenum/gold-catalyzed Meyer-Schuster-rearrangement of propargyl alcohols. 5-Phenylpent-l-en-3-on ... 

Although direct oleflnation of l,4-dien-3-ones is synthetically difficult, an indirect route is now available conversion of the carbonyl to the propargyl alcohol, followed by catalytic Meyer-Schuster rearrangement using vanadyl acetoacetate [VO(acac)2]. Asymmetric alkoxyallylation of aldehydes has been achieved using a combined carbocupration-zinc homologation-allylation reaction in one pot. ... 

Meyer-Schuster rearrangements of secondary and tertiary propargylic alcohols occur readily with PPh3AuNTf2, in the presence of 4-methoxyphenylboronic acid or 1 equiv. of methanol to give enones with high selectivity for the -alkene (Scheme 117). ... 

Both E- and Z-configured a-trifluoromethyl enones are accessible via a Meyer-Schuster-type rearrangement of propargylic alcohols (Scheme 13a) [43, 44]. Under copper catalysis, the is-configured enone is obtained. When adding a rhenium salt as co-catalyst, the Z-configured product forms preponderantly. A similar report shows... 

Scheme 16.44 Meyer-Schuster rearrangement of propargylic alcohols reported by Sheppard and coworkers.

As discussed above, Sheppard and coworkers reported a protocol for the gold-promoted Meyer-Schuster rearrangement of propargylic alcohols to a-p-unsaturated ketones, which made use of an alcohol as additive (Section 16.6.1). ° ° As part of their investigations, they found that when propargylic alcohols containing an acetal moiety were used as precursors, a... 

---