Meyer s reagent

Me er s test Bromocriptine mesilate is dissolved in methanol/water 3 10. After addition of one drop of diluted hydrochloric acid and one drop of Meyer s reagent (mercuric potassium iodide) and shaking, a white precipitate is produced. 

The alkaloids readily give a precipitate with Dragendorff s reagent, a concentration of 6 p.p.m. being just detectable. Meyer s reagent, on the other hand, is a very insensitive test (44). 

A modification of Meyer s oxazoline-facilitated methoxy substitution by organometallic reagents has been used to synthesize a biphenyl precursor of cannabinol. A one-pot hydrolysis of the oxazoline moiety, ether cleavage and cyclization yielded the lactone. Cannabinol resulted from the subsequent reaction with methylmagnesium iodide (Scheme 78) (82TL253). 

Thiiran intermediates were also obtained from carbonyl compounds by the use of thiomethylene transfer reagents. Sulfur extrusion yielded olefins. Meyers s methylthio-2-oxazoIine is representative of such reagents [305],... 

Oxidation. Meyers et aV used Saigo s reagent (1) for oxidation of the primary alcohol 2 to 3 (70.5% yield). The reaction was one step in the total synthesis of maysine (4). 

Scheme 30. Coupling of aryl electrophiles with aryl Grignard reagents Meyer s coupling [115] a) MeOTf,b) NaBH4,c) (COOH)2 Fuson s procedure [116b] d) Et20, C6H6...

M, Meyer s test W, Wagner s test T, TLC (Dragendorff s and/or Iodoplatinate spray reagent) Q, quaternary alkaloids. 

Other compounds may need FGl before disconnection. Meyer s heterocyclic reagent (21) is made from diol (20) in a Ritter reaction (Chapter 8) and this comes from a S-hydroxy ketone by reduction. Disconnection again reveals two molecules of the same compound. 

Fig. 1, shown for the imine of crotonaldehyde). From the favored complex (shown on the left), the R group of the organolithium reagent is then transferred to the less-hindered face of the double bond of the unsaturated imine. These additions are the enantioselective evolution of Meyers s chiral oxazoline and chiral imine chemistry (Sect. 1.1). 

Madelung synthesis (indole) 137 Marckwald cleavage, of furans 79 Marckwald synthesis (imidazole) 224 Meth-Cohn synthesis (quinoline) 402 Meyer s oxazoline method 183 Morin reaction 456 Mukaiyama reaction 380 Mukaiyama reagents 53, 380... 

Some studies on Meyer s route to chiral carboxylic acids (1, 1 2, 10) have revealed that stereoselectivity in the deprotonation of chiral oxazolines is very dependent on the particular base-solvent combination used. A further route to chiral acids is by alkylation (with primary halides) and subsequent hydrolysis of the bis-anionic species (1) derived from acid anhydrides and /-ephedrine. Chemical yields are in the range 50—70%, while optical yields are around 75%. A full report has appeared on the general approach to chiral acids by the Michael addition of Grignard reagents to oxazepinedione derivatives (2), also derived from /-ephedrine. Optical yields of 80—99% have been claimed (2,11 3, 27). 

---