Synthesis of asymmetrical aryl-tin compounds by cleavage of alkyl-tin bonds with sodium metal in liquid ammonia followed by SRN1 reactions with chloroarenes

Surefire generation of stannylpotassium: highly reactive stannyl anions and applications

Organometallic reagents such as organolithium and Grignard reagents have long been esteemed in chemical synthesis for their exceptional reactivity. In contrast, the application of their sodium and potassium counterparts has been comparatively sluggish, notwithstanding their augmented reactivity stemming from their heightened ionic character. This inertia persists due to the constrained accessibility of these heavy alkali metal reagents. In this study, our focus was directed towards devising a convenient and pragmatic approach for fabricating heavy alkali metal-based reagents, particularly those grounded in potassium. Herein, we present a novel, direct method for generating stannylpotassium (Sn-K) reagents through the simple combination of readily available silylstannanes and t-BuOK. Subsequently, the generated Sn-K reagents were effectively harnessed for stannylative substitution of aryl halides, furnishing an array of arylstannanes straightforwardly under transition metal-free conditions. This application distinctly underscores the potential utility of highly reactive Sn-K species, hitherto sparingly tapped into within the realm of synthetic organic chemistry. Furthermore, our investigation confirms that Sn-K reagents manifest notably superior reactivity compared with their well-established stannyllithium (Sn-Li) counterparts. This heightened reactivity can be ascribed to the increasing ionic character of Sn-K, which was supported by computational experiments.

Synthesis of Functionalized Diaryldimethylstannanes from the Me2Sn2- Dianion by SRN1 Reactions

[reaction: see text] The reaction of different ArCl with the Me(2)Sn(2)(-) dianion in liquid ammonia under irradiation afforded Ar(2)SnMe(2) in good yields (68-85%). The results obtained clearly indicate that the reaction proceeded through an S(RN)1 reaction. As a synthetic application of these Ar(2)SnMe(2), the homocoupling is described in the presence of Cu(NO(3))(2).2.5H(2)O to afford the biaryls. These reactions proceeded almost quantitatively.

A Novel Type of Nucleophilic Substitution Reactions on Nonactivated Aromatic Compounds and Benzene Itself with Trimethylsiliconide Anions

[reaction: see text]. The reaction of fluorobenzene with Me3Si- anion (1) in HMPA at room temperature surprisingly affords o- and p-fluorotrimethylsilylbenzenes (substitution of aromatic H for TMS, 76% yield) 7a and 7b and also 14% of trimethylsilylbenzene (2). Benzene itself reacts at 50 degrees C to furnish 4 in 45% yield. Pyridine affords p-trimethylsilylpyridine quantitatively. Mechanistic studies are presented.

Reactions of 1- and 2-Halo- and 1,2-Dichloroadamantanes with Nucleophiles by the S(RN)1 Mechanism

2-Bromoadamantane (2-BrAd) reacted in liquid ammonia under irradiation with diphenylphosphide (Ph(2)P(-)) ions whereas 2-chloroadamantane (2-ClAd) did not under the same experimental conditions. However, 2-ClAd yielded 2-(trimethylstannyl)adamantane in its photostimulated reaction with trimethylstannyl (Me(3)Sn(-)) ions. The compound 1-ClAd yielded the substitution product in a photostimulated slow reaction when the nucleophile is Ph(2)P(-) ion; the reaction occurs faster with the nucleophile Me(3)Sn(-) ion. All these reactions can be explained by the S(RN)1 mechanism as they did not occur in the dark and were inhibited by p-dinitrobenzene when photostimulated. In competition experiments, 1-haloadamantane showed more reactivity than 2-haloadamantane. Either with Ph(2)P(-) or Me(3)Sn(-) ions, 1-BrAd is 1.4 times more reactive than 2-BrAd while 1-ClAd is 12 times more reactive than 2-ClAd with Me(3)Sn(-) ions. In the photostimulated reaction of 1,2-dichloroadamantane (7) with Ph(2)P(-) the monosubstitution products 1-adamantyldiphenylphosphine (64%) and 2-adamantyldiphenylphosphine (15%) were formed, isolated as the oxides. From these results, it appears that when 7 receives an electron, the 1-position fragments ca. four times faster than the 2-position. The disubstitution product was not formed with Ph(2)P(-) ions, but when 7 reacted with a nucleophile having less steric bulk such as a Me(3)Sn(-) ion, the 2-chloro-1-(trimethylstannyl)adamantane and the disubstitution product 1,2-bis(trimethylstannyl)adamantane were formed. The formation of these products is explained in terms of the different rates of the electron transfer reactions of the radical anion intermediates.