Scheme III TBAF = (n-Bu)4NF Synthesis of /S-Furanone 2. Compound 1 (226 mg, 1 mmol) was dissolved in 8 mL of anhydrous diethyl ether, placed in a flask equipped with a dry argon inlet, and cooled at -15 °C. To the stirred solution was added 0.63 mL (1 mmol) of a 1.60 M ethereal solution of methyllithium. After 1.30 h at -15 °C, 1.5 mL of anhydrous hexamethylphosphoric triamide and 0.7 mL (8.8 mmol) of freshly distilled chloroacetyl chloride were added. The mixture was reacted 30 min at -15 °C and 1 h at room temperature.The reaction mixture was poured into a slurry of ammonia and crushed ice, stirred for 20 min, and then extracted three times with 20 mL of diethyl ether. The combined extracts were washed with water and dried (Na2S04). After evaporation at reduced pressure, 200 mg of product was obtained which was chromatographed on a Florisil (6 g) column. By elution with n-pentaneethyl acetate (95:5 v/v) there was obtained 160 mg (82% yield) of pure 2: oil; IR (liquid film) 1700,1640 cm"1; NMR (CDC13)4.50 (s, 2 H, OCH2CO), 0.95 (s, 9 H, (CH3)3C).

Physical model tests on cemented classified tailings and sand backfills have been carried out to determine the strength requirements for stability when vertical fill faces are exposed. The results of this laboratory scale model testing support a three-dimensional analytical solution developed in the paper, whereby the cement strength requirement can be reduced when rock walls are sufficiently close together to help support the backfill by shearing stresses at the wall-backfill contact.Comparisons with conventional backfill strength design approaches show that substantial reductions in cement usage can be realized by using the three-dimensional design approach, particularly when blast hole stoping can be carried out to heights several times greater than the lateral stoping dimensions.Physical modelling of cemented backfills is discussed in detail in the paper and it is concluded that field scale model testing could be useful in the design stages of the development of mining methods at individual mines.Des essais sur modtles physiques ont Ct C rCalisCs sur des stCriles classCs et des remplissages de sable cimentCs pour dtterminer les rksistrtnces requises pour assurer la stabilitC de faces verticales de remplissage. Les rCsultats de ces essais sur modkle en laboratoire concordent avec une solution analytique tri-dimensionnelle dCveloppCe dans l'article, selon laquelle la rksistance de cimentation requise peut Ctre rCduite lorsque les parois rocheuses sont suffisamment rapprochCes pour contribuer au support du remplissage par I'interrnCdiaire des contraintes de cisaillement au contact roc-remplissage.Les comparaisons avec les mCthodes usuelles de calcul de la rksistance de remplissages montrent que des reductions substantielles des quantitCs de ciment sont possibles en utilisant la mCthode tridimensionnelle, en particulier lorsque la hauteur des cheminCes est &gale 21 plusieurs fois leurs dimensions horizontales.La modelisation physique des remplissages cimentCs est discutCe en detail dans l'article et on en conclu que des essais sur modble sur le terrain pourraient Ctre utiles au stade de 1'Ctude des mCthodes d'exploitation de mines particulikres.

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