Methyl compounds

BH4 [69532-06-5]. The methyl compound has exhibited insertion reactivity, including aldehydes, ketones, nitriles, and isocyanides (29). Stable metaHacycle... 

The isolation of the 6-deoxytetracyclines (44) led to other chemical modifications of (1). 6P-Deoxytetracycline [5614-03-9] (13), prepared by catalytic hydrogenolysis of tetracycline (1), resulting ia an iaversion (45) of the configuration at the C-6 position, but retention of antibacterial activity. Catalytic reduction (7,8) of the 6-methylene derivative (14) yields both the 6a-methyl (15) and 6P-methyl compound (13). The 6a-isomer (15) is reported (7,45) to be more active than the 6P isomer (13). The a-isomer, doxycycline (6), is an example of a semisynthetic tetracycline that has become commercially useful. 

Methylstibonic acid, the only aLkylstibonic acid known with certainty, was not reported until 1990 (144). Previous attempts to obtain aLkylstibonic acids were unsuccessful (144). The methyl compound was prepared by two methods, the hydrolysis of a tetraaLkoxymethylantimony compound or the oxidation of dimethoxymethylstibine [54553-25-2], C3H202Sb, with hydrogen peroxide ... 

Discrimination between exposed and unexposed areas in this process requires the selection of thia zolidine compounds that do not readily undergo alkaline hydrolysis in the absence of silver ions. In a study of model compounds, the rates of hydrolysis of model /V-methyl thia zolidine and A/-octadecyl thiazolidine compounds were compared (47). An alkaline hydrolysis half-life of 33 min was reported for the /V-methyl compound, a half-life of 5525 min (3.8 days) was reported for the corresponding V/-octadecyl compound. Other factors affecting the kinetics include the particular silver ligand chosen and its concentration (48). Polaroid Spectra film introduced silver-assisted thiazolidine cleavage to produce the yellow dye image (49), a system subsequentiy used in 600 Plus and Polacolor Pro 100 films. 

Benzisoxazole and its simple alkyl derivatives are liquids with b.p. s of 84°C/11 mmHg for the unsubstituted system, 92.5°C/11 mmHg for the 3-methyl compound, and 117 °C/11 mmHg for the 4,6-dimethylbenzisoxazole. 2,1-Benzisoxazole is also a liquid, b.p. 94.4-94.5 °C/11 mmHg, and its 3-methyl derivative has a b.p. of 115.5-116 °C/11 mmHg. Introduction of a 3-phenyl substituent in both systems results in crystallinity, with m.p. s of 83-84 °C and 52-53 °C, respectively. Polar substituents, as anticipated, also impart crystallinity to these systems. 

Mass spectra of the same diaziridines were reported later (74JOU1140). Whereas in longer alkyl side chains of diaziridines the typical amine degradation by n -1 carbon atoms predominates, successive elimination of NH and methyl was observed in (37a). The 1-methyl compound (37b) undergoes competitive elimination of NH and MeN. 

The above data are correct to about 20 kJ mole but it will be seen that the general trend among these more covalent bonds does appear to be a decrease in stability from carbon to silicon, i.e. the same way as was found for more ionic bonds in the halides. Thermodynamic data for metallorganic methyl compounds used in the produchon of semiconductor systems are shown in Table 2.3. 

Most dienones that have been reduced have structures such that they cannot give epimeric products. However, reduction of 17 -hydroxy-7,17a-dimethyl-androsta-4,6-dien-3-one (63) affords 17 -hydroxy-7j9,17a-dimethylandrost-4-en-3-one (64), the thermodynamically most stable product, albeit in only 16% yield. The remainder of the reduction product was not identified. Presumably the same stereoelectronic factors that control protonation of the / -carbon of the allyl carbanion formed from an enone control the stereochemistry of the protonation of the (5-carbon of the dienyl carbanion formed from a linear dienone. The formation of the 7 -methyl compound from compound (63) would be expected on this basis. 

The 17i -hydroxy-16-ketone (47) on treatment with methylmagnesium bromide provides the 16a-methyl compound (48). ... 

The orally effective androgen 17a-methyltestosterone (51) is prepared from 3jS-hydroxyandrost-5-en-17-one (49) by treatment with methylmagnesium iodide to give the 17a-methyl compound (50) which is then oxidized to yield... 

Bromination of the enolate anion from the reaction of 3j -acetoxypregna-5,16-dien-20-one (1) with methylmagnesium bromide in the presence of cuprous chloride affords (after treatment with sodium iodide to dehalo-genate any 5,6-dibromide) a mixture of 17a-bromo- and 17)5-bromo-16a-methyl compounds (11) and (12) in a ratio 9 1. The 17a-iodides can be obtained in an analogous reaction. 

Application of the cuprous chloride-catalyzed conjugate Grignard addition to A -5a-3-ketones (13) gives la-methyl compounds (14) in yields up to... 

Grignard addition occurs towards the j5-face of the molecule with A -5)5-3-ketones (18) to form the axial lj5-methyl compounds (19). The reaction is not influenced by the presence of an 11a- or 1 l)5-hydroxyl group, an 11-ketone or a 9(1 l)-double bond. ... 

Acetoxy-4-chloroandrosta-l,4,6-trien-3-one and A -triene-3,l 1-di-ketones give analogous 1,4-additions to provide the la-methyl compounds. ... 

A reaction time of one hour at —7° to — 10°C was found to give maximum yields of 7a-methyl compounds. In some cases it is necessary to subject the reaction mixture to chloranil dehydrogenation this transforms (32) to the A -compound, thereby facilitating separation of the 7a-methyl isomer (31). The latter isomer is not attacked by the quinone since it lacks an axial hydrogen at C-7. 

In addition to the expected 2,2-dimethyl- and 2a-methyl- compounds (7) and (8) the 2 -methyl-3-ketone (9) is obtained. Chemical evidence and optical rotatory dispersion measurements indicate that ring A in (7) and (9) is in the boat conformation. 

Attempts to methylate the 6,11-diketone (12) under the conditions described above or with sodium hydride in benzene were unsuccessful. However, addition of methyl iodide to a refluxing suspension of sodium hydride in a solution of (12) in xylene affords the 5 -methyl compound (13) in about 37 % yield. ... 

Expulsion of nitrogen with formation of the A -l-methyl compound (9) occurs by heating (8) at ca. 220° or at room temperature by contact with acidic adsorbents. ° However, in this case perchloric acid or boron trifluoride etherate catalyzed fragmentation is not possible, although high yields (80 %) of (9) are obtained by heating (8) with quinoline or aniline. The la,2a-methylene compound (10) is always obtained as a by-product in 5% yield. 

High vacuum pyrolysis, heating in organic bases, contact with acidic adsorbents and reaction at room temperature with perchloric acid or boron trifluoride etherate cleaves the pyrazoline to give a 45-60% yield of the cyclopropane derivative (13) as well as 9 % of the unsaturated methyl compound (14). ° ... 

In A -3-keto-5jS-H steroids (7) the attack of the Corey reagent occurs towards the ) -face forming 1 j8,2j6-methylene-5) -H compounds (8). The / -configuration of the cyclopropane ring was established by conversion of (8) into the corresponding IjS-methyl compound. ... 

The acetoxy dienone (218) gives phenol (220). Here, an alternative primary photoreaction competes effectively with the dienone 1,5-bonding expulsion of the lOjS-acetoxy substituent and hydrogen uptake from the solvent (dioxane). In the case of the hydroxy analog (219) the two paths are balanced and products from both processes, phenol (220) and diketone (222), are isolated. In the formation of the spiro compound (222) rupture of the 1,10-bond in the dipolar intermediate (221) predominates over the normal electron transmission in aprotic solvents from the enolate moiety via the three-membered ring to the electron-deficient carbon. While in protic solvents and in 10-methyl compounds this process is inhibited by the protonation of the enolate system in the dipolar intermediate [cf. (202), (203)], proton elimination from the tertiary hydroxy group in (221) could reverse the efficiencies of the two oxygens as electron sources. 

Heating the 9-methyl-9aH-quinolizine (83) with 2-methylpyridine in methanol causes isomerization to the corresponding 9-methyl-4H-quinolizine (84), but with 3-methylpyridine the isomeric 7-methyl-4H-quinolizine (86) is obtained. Similarly the 9-methyl compound (83) and the corresponding 7,9-dimethyl derivative (82) with pyridine yield tetramethyl 47f-quinolizine-l,2,3,4-tetracarboxylate (78) with loss of the original alkylated pyridine. The mechanism of these reactions has not been established but the addition-elimination isomerization sequence for 3-methylpyridine accounts for the known cases of exchange of the pyridine (see Scheme 1). 

The analogous structures 309, 310, and 311 have been suggested for the pyrophthalones. Early work favored structure 309 (see reference 385 and references therein). Later, ultraviolet spectral data showed the presence of an extended conjugated system, and comparison with the spectra of the A -methyl compounds suggested structure 310. ... 

A number of alkyl and dialkyl (mainly methyl) benzofuroxans are known. The 4-methyl compound resisted attempts to brominate the methyl group and to oxidize it to the carboxylic acid. ... 

---