A variety of novel cage-functionalized pyridyl containing crown ethers have been prepared for use in selective alkali metal complexation studies. A highly preorganized, cage-functionalized cryptand also has been designed and has been synthesized for use as a selective Li+ complexant. The alkali metal picrate extraction profiles of these cage-functionalized crown ethers also have been studied. Novel cage-functionalized diazacrown ethers have been prepared for selective alkali metal complexation studies. Alkali metal picrate extraction experiments have been performed by using this new class of synthetic ionophores to investigate the effects of cage-annulation and the influence of N-pivot lariat sidearms upon their resulting complexation properties. Novel pyridyl containing calix[4]arene receptors were prepared. Analysis of their respective 1H NMR and 13C NMR spectra suggests that calix[4]arene moieties in the ligand occupy the cone conformation. The complexation properties of these host molecules were estimated by performing a series of alkali metal picrate extraction experiments. An optically active cage-functionalized crown ether which contains a binaphthyl moiety as the chiral unit was prepared. The ability of the resulting optically active crown ether to distinguish between enantiomers of guest ammonium ions (i.e., phenylethylamonium and phenylglycinate salts) in transport experiments was investigated. Hexacyclo[11.2.1.02,12.05,10.05,15.010,14]hexadeca-6,8-diene-4,11-dione was prepared from hexacyclo[7.4.2.01,9.03,7.04,14.06,15] pentadeca-10,12-diene-2,8-dione. Unanticipated but remarkable acid and base promoted rearrangements of this new cage dione to novel polycyclic systems were observed and subsequently were investigated. The structures of the new systems thereby obtained were determined unequivocally by application of X-ray crystallographic methods. It is noteworthy that the reactions reported herein each provide the corresponding rearranged product in high yield in a single synthetic step. Pi-facial and regioselectivity in the thermal Diels-Alder cycloaddition between hexacyclo[11.2.1.02,12.05,10.05,15.010,14]hexadeca-6,8-diene- 4,11-dione and ethyl propiolate have been explored. This reaction proceeds via stereospecific approach of the dienophile toward the syn face of the diene p -system. However, [4+2]cycloaddition proceeds with only modest proximal/distal regioselectivity. The structure of the minor reaction product was established unequivocally via application of X-ray crystallographic techniques.

First section of chapter 1 deals with gold catalyzed synthesis of ring fused furo[3,2,b]pyrans and furo[3,2,b]furans. Furo[3,2,b]pyrans and furo[3,2,b]furans are ubiquitous structural segments found in a number of natural products including polyether containing marine toxins. Synthesis of furo[3,2,b]pyrans 2a was accomplished from the bis-propargyl ethers 1a, while the synthesis of furo[3,2,b]furans 2b was accomplished from the prenyl propargyl ethers 1b. Scheme 1: Synthesis of furo[3,2,b]pyrans and furo[3,2,b]furans Second section of chapter 1 describes an unusual ring-contraction rearrangement route to functionalized 2,8-oxymethano-bridged di and triquinane. During the course of investigations concerning the total synthesis of 6-oxabicyclo[3.2.1]octane framework containing natural products, an unusual ring-contraction rearrangement sequence was observed in the reaction of 5-substituted 1-methyl-4-isopropenyl-6-oxabicyclo[3.2.1]octan-8-ones 4 to the 2,8-oxymethano-bridged diquinanes 5. The reaction was further demonstrated in the synthesis of triquinane 7 framework. Scheme 2: Synthesis of functionalized di and triquinane In third section of chapter 1 gold catalyzed synthesis of isochromanones and isoquinolones from suitable substituted allyl propargyl ethers was discussed. Synthesis of isochromanones and isoquinolones comprising a quaternary center with high diastereoselectivity was realized via AuCl3 catalyzed tandem intramolecular exo-dig heterocyclization/enol isomerization/Claisen rearrangement sequence in excellent yields. The reaction was general and amenable for the synthesis of structurally diverse analogues. Scheme 3: Synthesis of isochromanones and isoquinolones Forth section of chapter 1 consists of gold catalyzed intramolecular hydroalkoxylation assisted ring opening of furans to the corresponding saturated -keto esters. During the course investigations concerning gold catalyzed intramolecular enyne cyclization reactions, an interesting ring opening of furans in furyl propargyl alcohols to the corresponding tetrahydrofuran appended saturated -keto esters exclusively driven by intramolecular hydroalkoxylation of the alkyne was observed. Reaction of furyl propargyl alcohols without free hydroxyl group, under similar conditions afforded the conjugated enynes involving dehydration/ketalization. Scheme 4: Synthesis of saturated -keto esters and enynes Chapter 2 delineates the enantiospecific synthesis of bicyclo[4.2.2]decadienes 15 via gold catalyzed tandem enyne cyclization, semipinacol rearrangement reaction. Bicyclodecadienes are key structural units of natural products nakafuran-8 and pallescensin B. Scheme 5: Synthesis of bicyclo[4.2.2]decadienes