Similarity synthesis

A similar synthesis starts from commercially available 1,5-hexadiyne and 2-methyl-cyclopent-2-enone. The benzocyclobutene is obtained from a bis-acetylene in a cobalt-catalyzed reaction. It rearranges regio- and stereoselectively to a 3-deoxy steroid derivative. The overall yield from the cyclopentenone was 40% (R.L. Funk, 1977). 

R = SCH2CH2OCONH2, X = Na) [94392-35-5] (22) have been documented. Similarly, synthesis of the carbapenem antibiotic thienamycin [59995-64-1]... 

Aromatic denitrocyclizations have been used for many years in some well-known synthetic reactions. Probably the best known example is the Turpin synthesis of phenoxazines and similar synthesis of phenothiazines. The classical setup used usually base-catalyzed reactions in polar protic solvents, very often alcohols. In many cases using polar aprotic solvents was found advantageous. Besides the mentioned influence of the H-bonding, better ionization and lower solvation of the nucleophile are also important. Sf Ar reactions proceed through strongly polarized complexes, which are well soluble and highly polarized in polar aprotic solvents. 

The cyclized analog of meralluride is prepared by a similar synthesis. Thus, condensation of camphoric acid (42) (obtained by oxidation of camphor) with ammonia gives the bicyclic succinimide (44). Reaction with allyl isocyanate followed by ring opening and then reaction with mercuric acetate affords the mercury derivative (45) as the acetate rather than the hydroxide as above. Reaction with sodium chloride converts that acetate to the halide (46). Displacement on mercury with the disodium salt of thioglycollic acid affords the diuretic mercaptomerine (47). ... 

A similar synthesis starting with l-(2-nitrobenzyl)pyrrol-2-aldehyde used ethanol-ethyl acetate as solvent (62). Indoles are prepared in excellent yield by hydrogenation of o-nitrobenzyl ketones over Pd-on-C (i). Azaindoles are correspondingly prepared from nitropyridines (97). 

A similar synthesis of ruthenocene was done by neutron irradiation of FeCp2 and RUO2 powders together. The yield of RuCp2 was, however, extremely low (0.01 %)37).38>. K ,... 

Treatment of the 1,2-oxazines 52 with carbon monoxide at 1000 psi in the presence of cobalt carbonyl brings about insertion of carbon monoxide to form the 1,3-oxazepines S3 <96TL2713>. A convenient route to P-lactams fused to oxepines is made available by alkene metathesis. Thus reaction of 4-acetoxyazetidin-2-one with ally alcohol in the presence of zinc acetate, followed by iV-allylation of the nitrogen affords the derivative 54 which cyclises by RCM to form the oxazepinone 55 <96CC2231>. The same communication describes a similar synthesis of 1,3-dioxepines. 

Alkenyl sulfoxides (42 and 43) were first prepared in optically active form by Mulvaney and Ottaviani , described in an article overlooked by most workers in the field, and a year later by Stirling and coworkers through the reaction of the appropriate vinyl Grignard reagent with sulfinate ester 19. Both groups studied the addition of nucleophiles to the carbon-carbon double bond . More recently, Posner and coworkers reported a similar synthesis of ( )-l-alkenyl sulfoxides, e.g. 44 and In the synthesis of 45,... 

A similar synthesis starting from the derivatives of maltose (55), lactose (46), and cellobiose (57) to give the L-asparagine derivatives 56,48, and 58, respectively, was accomplished by Dunstan and Hough.46... 

Roberts et al. (1966) described a similar synthesis cyanoacetaldehyde and guanidine hydrochloride gave 40-80% yields of 2,4-diaminopyrimidine under the conditions of the lagoon model mentioned above. Hydrolysis of diaminopyrimi-dine leads to cytosine, isocytosine and uracil. Thiourea reacts with cyanoacetylene to give 2-thiocytosine however, the yield is considerably lower than with urea or... 

A similar synthesis of chiral (o-hydroxyaryl)oxazaphospholidine oxides 166a-b, 167a-b, and 169a-d derived from (5)-prolinol 127 and its diphenyl derivative 163 was achieved from precursors 164a-b, 165a-b, and 168 which were easily available from two different procedures as outlined in Scheme 46 [77], The first pathway gave the two expected diastereomers of 164 and 165 in a ratio... 

Reddy et al. [54] performed a rather similar synthesis of trifluoromethyl aryl-diazepines 38 and 39 by the reaction of o-aryldiamines 35 with the synthon 37 (Scheme 4.19). 

The indole compound was described by Flynn et al. [73] and is prepared in a similar manner as the thiophene 103 and furan 108. One method involved a similar synthesis as described in Scheme 25, using the relevant starting material. However, an alternative synthesis involved a one-pot, room-temperature synthesis, Scheme 27. The o-iodotrifluoroacetanilide 110 was coupled to the alkyne 111 under Sonogashira conditions in MeCN. K2CO3 and the aryliodo compound 107 was added and the reaction stirred to produce the protected product 112 with a 77% yield. Deprotection to the corresponding phenol 113 was performed using AICI3. 

To try and address this issue of conformation, Forrest et al., in the authors laboratory examined methyl- and phenyl-substituted analogs of the pyrazoles mentioned above, employing a similar synthesis [91]. These molecules are... 

Shortly after the above work appeared, Bolliger and Prins90 reported a similar synthesis leading to a 3- rather than a 2-desoxy derivative. Methyl 2,3-anhydro-4,6-benzylidene-a-D-mannoside (LXIV), upon treatment with sodium thiomethoxide, was converted into methyl 3-methyl-thio-4,6-benzylidene-a-D-altroside (LXV) which, after desulfurization and rebenzylidenation, gave methyl 3-desoxy-4,6-benzylidene-a-D-man-noside (LXVI). Methylation of LXV with methyl iodide and silver oxide followed by desulfurization gave methyl 2-methyl-3-desoxy-4,6-benzylidene-a-D-mannoside in poor yield. 

A second similar synthesis, due to Doebner and Miller, leads to the formation of substituted quinolines. The simplest example is the production of quinaldine from aniline and paraldehyde by heating with concentrated hydrochloric acid. The course of the reaction is closely related to that of the Skraup synthesis by route II. There the aniline reacts with acrolein, here with crotonaldehyde, which is easily formed under the conditions which prevail ... 

The formation of l-lithio-.io so. si.ssi 2.iithio-, and 3-lithiodibenzothiophene has been achieved by translithiation of the appropriate bromodibenzothiophene (Section VI, C, 3) with butyllithium. Higher yields of derivatives are obtained from 2-lithiodibenzothiophene by conducting the reactions at 0° rather than at room temperature. The comparatively low yield of compounds derived from 3-lithiodibenzothiophene at 0° may indicate that even lower reaction temperatures are required for this particular isomer, reduced yields probably being due to ortho-translithiation to the thermally stable 4-lithiodibenzothiophene (cf. the instability of 3-lithio-benzo[6]thiophene at 0° ). Both 2-lithio- and 3-lithio-4-methyldibenzo-thiophene have been prepared from the respective bromo compound, and a similar synthesis of 1 -lithio-4-methoxydibenzothiophene has been described. ... 

The synthesis of TNAZ (18) via the electrophilic addition of NO+NO2 across the C(3)-N bond of l-azabicyclo[1.1.0]butane (26) was found to be very low yielding ( 1 %) and impractical. Nagao and workers reported a similar synthesis of TNAZ via this route but the overall yield was low. 

Similar synthesis of l-hydroxypyrazole-2-oxides was realized in the presence of Co(II) ions or HN02 as nitrosating agent. Pyrazole-Af-oxides were successfully obtained from 1,3-dioximes and SOCI2 . 

This is a similar synthesis in which the ring atoms are assembled by reacting a 1,3-dicarbonyl compound with cyanoacetamide (cyanoethanamide)... 

Azides [e.g. (+)-neomenthyl azide no physical data reported] are formed efficiently by inversion, from the corresponding alcohols and diphenylphosphoryl azide, in the presence of triphenylphosphine and diethyl azodicarboxylate [which has also been used for esterification with inversion (Vol. 5, p. 334) for a related esterification of (—)-menthol see ref. 119] a conceptually similar synthesis also yields (+)-neomenthyl azide. Cyanoselenenylation of aldehydes and of alcohols has been reported thus treatment of geraniol with o-nitrophenyl seleno-cyanide-Bu sP-THF yields the selenide (19) which can be converted into the... 

When 2 -methoxy-2-biphenylamine is diazotized in fluoroboric acid, an 85% yield of solid 2 -methoxy-2-biphenylyldiazonium tetrafluoroborate is produced. On heating in dry benzene, this salt loses nitrogen and provides 0-methyldibenzofuranium tetrafluoroborate as an unstable solid. The latter salt, on account of the low basicity of dibenzofuran, reacts with a range of nucleophiles that undergo methylation with the release of dibenzofuran. Pyridine and pentachloropyridine are N-methylated, benzo[fc]thiophene is S-methylated, and tetrahydrofuran and phenetole are 0-methylated. ° Thus it is no surprise that diazotization of 2 -methoxy-2-biphenylamine, followed by boiling of the diazonium salt in acidic solution, provides dibenzofuran in 90% yield.The scope of this method of dibenzofuran synthesis (Scheme 18) has been little explored probably because of the difficulty of preparing the requisite biphenyls, which is usually accomplished by a crossed Ullmann reaction. A similar synthesis of xanthones from 2-amino-2 -methoxybenzophenones is known. ° ... 

A similar synthesis of mechanistic interest rather than preparative value involves the thermal reaction of dimethyl 2,5-bisdiazo-3,4-diketoadipate (89, Scheme 23) with benzofuran (91)." The presumed intermediate is the pyrone cation 90 produced from the adipate 89 by the Wolff rearrangement, cyclization, and loss of nitrogen. Electrophilic substitution then affords the benzofuran 92, which can be isolated. Ring opening and cyclization of the resultant ketene 93 then affords the dibenzofuran 94 in poor (0.4%) yield. 

A novel synthesis in which diazoketones are thermolyzed with JV-sul-finylamines leads to cyclic S-oxides such as 3,4-dihydro-1,2,3-oxathiazine and 1,2-oxazetidine derivatives. A similar synthesis utilizing diazodiketones yields, via a 4 -f 2 cycloaddition, oxathiazines (165) and, via 2 -F 2 cycliza-tion, thiazetidines (166). When sulfonyldiazoketones were used, thiazetidines 167 were the only isolated products (Eq. 33). 

Similar synthesis with acrylonitrile has been described by the following reaction scheme ... 

Several similar synthesis processes have been described in the literature that lead to particles of up to 10 p.m (38,46-49). The formation of larger particles is based in all those processes on the hydrolysis of alkoxysilanes and the deposition of silica onto previously prepared seed particles. 

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