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A tin(IV) chloride promoted (3 + 2) annulation of trans-2-aroyl-3-styrylcyclopropane-1,1-dicarboxylates with nitriles is reported. The transformation involves the Lewis acid assisted formation of 1,5-dipolar intermediates from the cyclopropane dicarboxylates and nitriles followed by cyclization. The reactions proceed in a highly diastereoselective manner and afford 5-vinyl-1-pyrroline derivatives in 60–88% yields.

The allyltin trichloride formed by treating [(4S)-5-(tert-butyldimethylsilyloxy)-4-(2-trimethylsilylethoxy methoxy)]pent-2-enyl(tributyl)stannane 9 with tin(IV) chloride, reacts stereoselectively with 2-oxoethyl toluene-p-sulfonate to give the syn-6-(2-trimethylsilylethoxymethoxy)hept-4-en-2-ol 10 which was converted into the epoxide 11 by treatment with potassium carbonate in methanol. After replacing the tert-butyldimethylsilyl ether by a benzyl ether, removal of the 2-trimethylsilylethoxymethoxy group using trifluoroacetic acid, gave the 2,6-cis- and 2,6-trans-disubstituted 5,6-dihydro-2H-pyrans 14 and 15, ratio 80:20, which were separated as their tert-butyldimethylsilyl ethers 16 and 17 and characterised as their acetates 18 and 19. The 5,6-dihydro-2H-pyrans 24 and 26, ratio 80:20, were similarly prepared from (4S)-4-(2-trimethylsilylethoxymethoxy)pent-2-enyl(tributyl)stannane 21. A complementary route to the trans-2,6-disubstituted 5,6-dihydro-2H-pyran 15 was developed from 2-oxoethyl benzoate which gave the syn-hydroxy ether 28 under the usual conditions. Mesylation and ester saponification gave the anti-epoxide 30 and, after replacing the tert-butyldimethylsilyl ether by a benzyl ether, treatment with trifluoroacetic acid gave the 5,6-dihydro-2H-pyrans 14 and 15, in favour of the trans-isomer, ratio 14:15= 20:80. Improved stereoselectivity in these dihydropyran syntheses was obtained if the stannane 9 was treated with butyl glyoxylate in the first step. The cis-2,6-disubstituted 5,6-dihydro-2H-pyran 16 was converted into the tetrahydropyran-3-one 37 by hydroboration–oxidation, and into the tetrahydropyran-4-one 43 by treatment with bromine water, reductive debromination and oxidation.

[(4S)-5-(tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl](tributyl)stannane 18 has been prepared from di-O-isopropylidene-D-mannitol 8. Oxidative cleavage of the mannitol derivative followed by condensation with triethyl phosphonoacetate and reduction gave the alcohol 10 which was converted into the xanthate 11. Deprotection gave the dihydroxy xanthate 12 which was protected as its bis-tert-butyldimethylsilyl ether 13. This rearranged on heating in toluene to give the dithiocarbonate 15 which reacted with tributyltin hydride under free radical conditions to give the [(4S)-4,5-bis(tert-butyldimethylsilyloxy)pent-2-enyl](tributyl)stannane 16 as an approximately 9:1 mixture of E- and Z-isomers. Deprotection and selective protection of the primary hydroxy group provided the [(4S)-5-(tert-butyldimethylsilyloxy)-4-hydroxypent-2-enyl]stannane 18. As a shorter route, the primary hydroxy group of the dihydroxy xanthate 12 was protected as its tert-butyldimethylsilyl ether 14 which underwent clean rearrangement into the dithiocarbonate 19 when heated in toluene. Reaction with tributyltin hydride under free radical conditions then gave the (5-tert-butyldimethylsilyloxy-4-hydroxypent-2-enyl)stannane 18. Treatment of this 4,5-disubstituted pentenylstannane with tin(IV) chloride generated an allyltin trichloride which reacted with aldehydes with excellent 1,5-asymmetric induction to give 1,5-syn-products, e.g. 20, 29–31 and 41. The stereoselectivity of these reactions would appear to be controlled by the 4-hydroxy substituent rather than by the 5-tert-butyldimethylsilyl group. Aspects of the chemistry of these products, in particular their conversion into 2,6-disubstituted 5,6-dihydro-2H-pyrans, was investigated.

The Sn–Cl distances in octahedral SnCl4L2 compounds are linearly related to the Mossbauer partial quadrupole splitting data; the correlation can be used to predict Sn–Cl distances, and has allowed us to detect an error in the published crystal structure of tetrachlorobis(1,3-diethylthiourea)tin(IV) which was confirmed in a redetermination.

Dielectric absorption measurements (over the frequency range 1–36 GHz) of the system tin(IV) chloride–benzene indicate that most of the polar properties are due to the presence of moisture. The intensity of the dielectric relaxation process depends on the amount of water present, but the observed relaxation time is independent of the water concentration.

The kinetics have been measured for the rearrangement of 1-phenylprop-2-en-1-ol (1) to 3-phenylprop-2-en-1-ol (2) in tetramethylene sulphone solution, catalysed by various tin(IV) chloride species. The rate coefficients, kn′ at 313.2 K, per unit concentration of the catalyst, were: SnCl4, 305; PhSnCl3, 86.4; p-MeC6H4SnCl3, 18.7; MeSnCl3, 6.60; PrnSnCl3, 5.36; EtSnCl3, 4.69; BunSnCl3, 1.62; (p-CIC6H4)2SnCl2, ca. 3 × 10–2; Ph2SnCl2, 5.1 × 10–3; Et2SnCl2, 1.4 × 10–3, Me2SnCl2, 4.3 × 10–4 dm3 mol–1 s–1. The reaction catalysed by SnCl4 was studied with a range of added compounds, viz. H2O, LiCl, LiCIO4, and 1,8-bis(dimethylamino)naphthalene. Evidence was obtained for the involvement of both anhydrous SnCl4 and its monohydrate as catalysts for the rearrangement. Tin(II) chloride has been found to be an effective catalyst for the rearrangement, with kn(313.2 K)= 3.51 dm3 mol–1 s–1. Addition of phosphoryl chloride to SnCl2 causes a sharp increase in rate, with a maximum corresponding to the species SnCl2·POCl3. The value of kn(303.5 K)≃ 1 200 dm3 mol–1 s–1 makes this catalyst the most powerful yet found for the rearrangement.

The 35Cl n.q.r. spectra of a series of tin(IV) chloride adducts SnCl4·2L [L = MeCN, CH2CHCN, ButCN, PhCN′ CH2(CN)2, 1,2-C6H4(CN)2, SMe2O, or tht (tetrahydrothiophen)] have been recorded at various temperatures and used to deduce whether these complexes are cis or trans. A trans structure is indicated for SnCl4·2tht, cis structures for the remainder. When compared with other published n.q.r. and structural data, our results indicate that the 35Cl n.q.r. frequencies are related to the Sn–Cl bond lengths in such systems. The higher 35Cl n.q.r. frequencies tend to be associated with the shorter bonds, though the frequencies also vary markedly with temperature.

1,1,3,3-Tetramethyl-1,3-disilacyclobutane, (I), reacts with trichlorosilane or dichloro(methyl)silane in the presence of hexachloroplatinic(IV) acid to give the chlorine-exchange adducts, Me2SiCl·CH2·SiMe2·CH2·SiHCl2(80%) or Me2SiCl·CH2·SiMe2·CH2·SiMeHCl (61%); in the latter reaction the hydrogen-exchange adduct, Me2SiH·CH2·SiMe2·CH2·SiMeCl2(5%). is also formed. A comparable reaction of 1.3-dimethyl-1.3-diphenyl-1,3-disilacyclobutane, (II), with trichlorosilane gives mainly polymeric material together with the chlorine-exchange adduct (10%). Both silacyclobutanes react with tin(IV) chloride in the absence of catalyst or with trimethylsilanol to afford ring-opened 1 :1 adducts in high yield. Compound (I) also reacts with triphenylsilanol to afford hexaphenyldisiloxane and 1,1,3,3-tetramethyl-1,3-bis(trimethylsilylmethyl)disiloxane (87%); (II) does not react under comparable conditions.

The reactions between SnCl4 and (SiH3)nX have been investigated [n= 1, X = H, F, Cl, Br, SiH3, Mn(CO)5, or Co(CO)4; n= 2, X = 0 or S; n= 3, X = N or P]; the reaction with (Me2SiH)2O was also investigated. With SiH4, Si2H6, SiH3F, SiH3Cl, [SiH3Mn(CO)5], and (SiH3)3N, reaction led to monochlorination at silicon, and spectroscopic parameters for the compounds SiH2FCl, [SiH2ClMn(CO)5], ClSiH2N(SiH3)2, (ClSiH2)2NSiH3, and (ClSiH2)3N, all prepared by this route, are reported. For the amines, 29Si and 15N chemical shifts were measured by heteronuclear double resonance. Reactions with other silyl compounds led to the formation of SiH3Cl, although some evidence was obtained for the formation of intermediate trichlorostannyl species.