Diazomethane, trimethylsilyl cycloaddition reaction

More recently, [2+3] cycloaddition reaction of the tri-te/t-butylphenylphosphaethyne (25) has been reinvestigated, when in spite of the steric encumbrance of extremely bulky Mes group, the use of trimethylsilylated diazomethane (24) makes its cycloaddition successful, which is followed by SiMe3/H migration yielding bulky [l,2,4]diazaphospholes [33], Phosphaalkyne 25 reacts with 24 in a regioselective manner to form intermediate cycloadduct 26, which undergoes facile aromatization... 

Diazo compounds have also been used as precursors in the preparation of pyrazoles and indazoles. The copper-promoted cycloaddition reaction of lithium acetylides 18 with diazocarbonyl compounds 19 provided a direct and efficient approach to the synthesis of pyrazoles 20 <07AG(I)3242>. A facile, efficient, and general method for the synthesis of 1-arylated indazoles 22 and A-unsubstituted indazoles 23 by the 1,3-dipolar cycloaddition of benzynes, generated from 21, with diazomethane derivatives has been reported <07AG(I)3323>. Reaction of diazo(trimethylsilyl)methylmagnesium bromide with aldehydes or ketones gave 2-diazo-2-(trimethylsilyl)ethanols, which were applied to the synthesis of di- and trisubstituted pyrazoles via [3+2] cycloaddition reaction with ethyl propiolate or dimethyl acetylenedicarboxylate <07S3371>. 

A theoretical study of the intermediates involved in the formation of phospha-propyne from pyrolysis of vinylphosphirane has led to a new route to phospha-alkynes. Thus, pyrolysis of trimethylsilyl(l-phosphiranyl)diazomethane has yielded MeaSiC = P, via an intermediate 1-phosphiranylmethylene . Regioselec-tivity in the [3 + 2] cycloaddition reaction between phosphaethyne and diazomethane has been studied by theoretical techniques , and further examples of reactions of this type described . Cycloaddition of phospha-alkynes with silylenes has also been reported. The primary phosphine 324 has been isolated from the addition of diethylphosphite to t-butylphosphaethyne. The chemistry of phospha-alkyne cyclotetramer systems has been reviewed and the first examples of platinum(II) complexes of such cage systems described. Aspects of the reactivity of coordinated phospha-alkynes have received further study, and a remarkable metal-mediated double reduction of t-butylphosphaethyne to the complexed fluorophosphine 325 described Phosphorus-carbon-aluminium cage structures have been isolated from the reactions of kinetically stable phospha-alkynes with trialkylaluminium compounds and new phosphaborane systems have been obtained from the reactions of phospha-alkynes with polyhedral boranes . Further studies of wo-phospha-alkyne coordination chemistry have appeared . The reactivity of the ion 326 has been explored. ... 

Whitlock, G.A. and Carreira, E.M. (1997) Enantioselective synthesis of ent-stellettamide A via a novel dipolar cycloaddition reaction of (trimethylsilyl)diazomethane. J. Org. Chem., 62,7916-7917. 

A very similar reaction to that of Pechmann and Nold but which probably does not proceed through a dipolar cycloaddition manifold is the formation of 1,2,3-thiadiazole (6) via a thionoester and lithium trimethylsilyldiazomethane (Equation (17)) <86H(24)589>. Lithium trimethylsilyl-diazomethane also reacts with thioketones to produce 1,2,3-thiadiazoles <87H(26)1467>. 

A further example of the diazaphosphole synthesis by [3 + 2] cycloaddition is given by the reaction of a phosphoranediyl diazomethane (26) (R = NPr j) with P-chloro-bis(trimethylsilyl)-phosphaethene. The adduct loses trimethylchlorosilane and yields a 3-phosphoranediyl-l,2,4-diazaphosphole (or 3-phosphonio-l,2,4-diazaphospholide) (27). The analogous addition to the trimethylsilyl substituted P-chloro-bis(methylene)phosphorane (28) yields a 4-methylene derivative (29) of this diazaphosphole (molecular structure in Table 1). It provides the only fully characterized example of this type up to 1995. Methyl triflate methylates the compound at N-1 and gives a phosphonio methylene diazaphosphole cation (30). 

By employing ortho-(trimethylsilyl)aryl triflates as benzyne precursors, Jin and Yamamoto have reported the synthesis of indazoles under mild reaction conditions by the [3-1-2] cycloaddition of benzyne with diazomethane derivatives, followed by a 1,3-hydrogen shift (Scheme 12.54) [103]. Depending on the stoichiometry of the reagents and the reaction conditions, either 1-arylindazoles 194 or IH-inda-zoles 195 are readily produced in fair to good yields. 

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