With Protic Acids

Protic acids HX with pKa less than about 25 cleave the Sn-N bond by reaction 16-29. SnNR2 + HX ------- SnX + HNR2 (16-29) 

These reactions occur more readily than with the Sn-OR or Sn-OSn bonds they often provide useful syntheses under mild conditions of the products SnX, and these reactions are discussed in the sections dealing with those compounds. 

Hydrolysis occurs very readily to give the organotin hydroxides or oxides, and the stannylamines must be prepared, stored and handled under dry, CC -free, conditions. The organotin derivatives of pyrrole are less sensitive, and their hydrolysis is reversible.3 Alcoholysis of the aminostannanes provides a clean route under mild conditions to the 

The reactions with hydrogen cyanide, hydrazoic acid, phosphines, and arsines (Section 16.5) have been used as routes to the organotin cyanides, azides, phosphines and arsines, respectively. Examples are given in the following equations.29 

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A simple acid-catalyzed cyclization transforms i//-ionone into n-ionone (W. Kimel, 1957, 1958). Further treatment with protic acids transforms the tr-ionone to the thermodynamically more stable -ionone. 

These phosphaalkenes are extremely reactive, they undergo facile [2 + 4] cycloaddition reactions (equation 39) or reactions with protic acids... 

A series of a-telluranes 44 with X = F, ONO2, OCOMe, and OCOCF3 were prepared by a treatment of the ylides 46 [82DOK(266)1164 85KGS757] or the telluroxides 47 (85KGS757) with protic acids. 

The authors used a synthesis of 9,9-spirobitluorenes 32 which was developed by Clarksen and Gomberg [60] and which includes the addition of biphenyl-2-yl-magnesium iodide to fluorenone and subsequent cyclization with protic acids. To obtain 2,2,, 7,7 -arylated 9,9-spirobifluorenes 33, 9,9-spirobifluorene (32) was tetrabrominated [58] to yield 34 followed by a Suzuki-type aryl-aryl cross-coupling with various oligoaryl and oligoheteroaryl boronic acids to obtain the 2,2, 7,7 -tetraarylated derivatives 33. 

In the base-assisted reactions, the hydrogenolysis products are recovered as sodium or potassium thiolates which can either be converted to thiols by acidification with protic acids, or be oxidized to disulfides by exposure to air.184,195 In turn, all of the Rh catalyst of the aqueous biphasic reactions remains in the polar phase for use in a further catalytic run after the thiolate product is extracted as thiol. 

Furylcarbinols with protic acids (fluoroboric acid) may merely give car-benium (furylium) salts.171 Similar cations are accessible via 2-furyldiazo-methane derivatives,172 but in many cases ring opening and prototropic shifts ensue as in Marckwald reactions (Scheme 30).173 A recent development controls solution acidity by using magnesium or zinc ions instead of protons... 

Studies reveal an advantage to using boron trifluoride in dichloromethane at reduced temperatures instead of Brpnsted acids in the organosilicon hydride reductions of a number of dialkylbenzyl alcohols.126 129 The use of Brpnsted acids may be unsatisfactory under conditions in which the starting alcohol suffers rapid skeletal rearrangement and elimination upon contact with the acid, and also in which the alcohol does not yield a sufficient concentration of the intermediate carbocation when treated with protic acids.126... 

Aqueous solutions of strong soluble bases (1) have a bitter taste, (2) have a slippery feeling, (3) change the colors of many acid-base indicators, (4) react with protic acids (acids that have an H) to form salts and water, and (5) conduct an electrical current since they contain ions. 

Aqueous ammonia reacts with protic acids to form salts (and no water), but exhibits all the other traits to a lesser degree since it is a weak base exhibiting limited ionization and providing a lower OH- concentration. 

As indicated under section 2.2. the overall result is the same as that of an insertion reaction, the difference being that insertion gives rise to a yw-addition and nucleophilic attack to an anri-addition. Sometimes the two reaction types are called inner sphere and outer sphere attack. There is ample proof for the anti fashion the organic fragment can be freed from the complex by treatment with protic acids and the organic product can be analysed [19], Appropriately substituted alkenes will show the syn or anti fashion of the addition. The addition reaction of this type is the key-step in the Wacker-type processes catalysed by palladium. 

Cationic polymerizations can be initiated with protic acids (e.g., sulfuric, perchloric, trifluoroacetic acid), with Lewis acids (see Sect. 3.2.1.1), and with compounds that form suitable cations (e.g., iodine, acetyl perchlorate). Some monomers are also polymerized by high-energy radiation according to a cationic mechanism. 

Examples of reactions of the carbon-carbon double bond of thietes with protic acids are... 

The 2,4-pentanedionato or acetylacetonato (acac) complexes are useful synthetic intermediates because they react with protic acids through the reaction (l) 1... 

Examples of reactions of the carbon-carbon double bond of thietes with protic acids are illustrated by the formation of mercaptoaldehyde (42) (72JOC1111), hydrogen cyanide adduct (43) (77JOC3506) and sulfide (44) (62JA399). 

Dialkylgold(III) dimers were produced (226, 227) by treatment of trial-kylgold(III) complexes with protic acids at low temperatures, the preparation being accompanied by elimination of alkane. 

Complexes such as cis-[Mo(N2)2(PMe2Ph)4 react with protic acids in nonaqueous solvents to give ammonia and hydrazine in yields which depend upon the complex, the solvent, and the acid employed (18, 103, 190, 320), for example, reaction (42). 

We have a choice of reagents for the -butyl cation a halide with Lewis acid catalysis, and -butanol or isobutene with protic acid catalysis. The least wasteful is the alkene as nothing is lost. Protonation gives the r-butyl cation and two r-butyl groups are added in one operation.3... 

The reactions of protic acids and other electrophiles at remote Lewis basic functionality have been investigated as a pathway to both transformations and interconversions of carbonyl-substituted metallacycles. Irida-, pallada-, and platinacyclobutanones react reversibly with protic acid to yield 73-2-hydroxyallyl complexes (Equation 36), modulating between metallacyclobutane and hydroxyallyl structures (and further discussed in Section 2.12.9.3.5) <1993CC1039, 1995JOM143, 19970M1159>. 

In other cases substituents compete by directing to different positions. For example, in the synthesis of the food preservative BHT (p. 30) from 4-methylphenol (p-cresol) by a Friedel-Crafts alkylation, the methyl and OH groups each direct ortho to themselves. The -OH group is much more powerfully directing than the methyl group because it provides an extra pair of electrons, so it wins and directs the electrophile (a t-butyl cation) ortho to itself. The t-butyl cation can be made from the alkene or t-butanol with protic acid or from t-butyl chloride with AICI3. 

Diphenyl ketene reacts with 39 to yield what has been described as a metal-anchored olefin complex (40) (109). The latter contains a diphenyl ketene ligand which is tj2-C,0 (a metallocyclopropene) -bonded to the (r)-C5H5)2Ti unit. Upon treatment of 40 with protic acids, carbon mon-... 

Like the 1,3-dithianes, 1,3-oxathianes can be metallated with alkyllithium reagents and they hydrolyse about 10,000 times faster with protic acids. However, their value is diminished by the limited stability of the lithio derivatives and their inherent lack of symmetry which introduces the complications of diaster-eoisomerism. Eliel and co-workers have exploited the diastereoisomerism of... 

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