Lactones benzannulated

Abstract The photoinduced reactions of metal carbene complexes, particularly Group 6 Fischer carbenes, are comprehensively presented in this chapter with a complete listing of published examples. A majority of these processes involve CO insertion to produce species that have ketene-like reactivity. Cyclo addition reactions presented include reaction with imines to form /1-lactams, with alkenes to form cyclobutanones, with aldehydes to form /1-lactones, and with azoarenes to form diazetidinones. Photoinduced benzannulation processes are included. Reactions involving nucleophilic attack to form esters, amino acids, peptides, allenes, acylated arenes, and aza-Cope rearrangement products are detailed. A number of photoinduced reactions of carbenes do not involve CO insertion. These include reactions with sulfur ylides and sulfilimines, cyclopropanation, 1,3-dipolar cycloadditions, and acyl migrations. 

A highly efficient synthesis of l-alkylidene-l,3-dihydrobenzo[f]furans from t>-hydroxymethyl iodoarenes and propargyl alcohols uses a bimetallic Pd/Cu-catalyzed Sonogashira coupling/cyclization reaction (Equation 132) <1999SL456>. Pd/l,4-bis(diphenylphosphino)butane (DPPB)-catalyzed reaction of t>-allylphenols under a CO atmosphere leads to carbonylative cyclization to form benzannulated lactones <2006ASC1855>. A similar carbonylative cyclization leads to the stereoselective formation of 3-alkenyl phthalides <2006T4563>. 

Gamble, R. C., Mitchell, L. H., Rutledge, P. S. Acid-promoted Fries rearrangements of benzannulated lactones. Aust. J. Chem. 1998, 51, 1167-1174. 

Geier. M.. and Hesse, M., Benzannulated lactones by ring enlargement, Synthesis, 56, 1990. El-Hossini. M.S., McCullough, K.J., McKay, R., and Proctor, G.R., Ring-expansion by a Wittig-Prevost sequence, Tetrahedron Lett., 27, 3783, 1986. 

Cyclobutanone cleavage. Benzannulated lactones are obtained from 2-(o-hydroxyphenyl)cyclobutanones as a result of Rh insertion. Whether the benzylic position is fully substituted is a determinant factor for giving rise to -y-lactones or c-lactones. 

Benzofurans and substituted indoles undergo epoxidation, but the products rearrange readily to give benzannulated lactones and lactams. Furan itself is converted to malealdehyde," which can be trapped by Wittig reagents. 

The resorcylic acid lactones (RALs) are a family of benzannulated macrolides, which are produced by a variety of fungi and show versatile biological activities (6). According to their name, they consist structurally of a partially substituted p-resorcylic acid scaffold, which is linked to a 12- or 14-membered macrolactone moiety. Selected members of this group are shown in Fig. 9.1. 

The vinylcarbene complexes Cr(CX))5 =C(OEt)C=CXR) (X = NMe2, OEt R = alkyl, aryl) react with alkynes R OCH to form various cyclopenta[b]pyrans.30S In a two step process, addition of the alkynes NEt20Chfe u> the l-metalla-l,3-diene W(CX))s =C(OEt)CHsCHHi) results in metallatriene species that cyclise U) fwm cyclopentadiene complexes 40. Chromium Fischer type alkoxyalkenyl carbene complexes react with ketoalkynes to fcxm bicyclic lactones in a number of different processes involving 8 and 10-e cyclizations. Various dienyl carbene complexes whose parent in Crortho-substituted aromatic alcohols through a variation upon the more usual benzannulation reaction involving alkyne cycloaddition with carbene complexes. ... 

Nishii et al. reported metal-mediated benzannulation reaction of diaryl(gm-dichlorocyclopropyl)methanols to synthesize unsymmetrically substituted a-arylnaphthalenes [61]. In particular. The reaction of optically active alcohol 145 in the presence of 1 equiv of HCU at —78 °C afforded chiral biaryl 146 with an excellent level of stereo induction (Scheme 27.48) [62]. It should be noted that chi-raUty exchange from sp central chiraUty to axial chirality takes place in this process. This methodology has been employed successfully for total synthesis of natural lignin lactones, justicidin B, and dehydrodesoxypodophyllotoxin (Scheme 27.49) [63]. 

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