S. R. Raychaudhuri

Efficient syntheses of some 1-naphthylalkyl ketones and studies on their autooxidation in basic medium

Abstract Birch reductions of 4,6-dimethoxy-1-naphthylalkyl ketones 1 provided in fair to good yields the demethoxylated products, 6-methoxy-1-naphthylalkyl ketones 2(a–g), not easily accessible by other procedures. Autooxidation of these ketones in basic medium afforded the diketones 6(a–c), the acid 2h, and interestingly the phenol 5. Extension of this reduction to the related tricyclic ketone 8 afforded 9a, the phenolic ketone 9b; and significantly the dihydrocoumarin derivative 10 as a result of autooxidation of 9a. The mechanisms for demethoxylation and autooxidation have been discussed.

Role of remote heteroatoms and nature of the reducing agents on the stereochemical course of reductions of the carbon–nitrogen π-bond of a new class of tetrahydropyridines

Total syntheses of the tetrahydropyridine derivatives (3a–f) and the steroid analogue (1b) are reported. Catalytic reductions of the above imines have been found to be highly stereoselective, yielding only the trans-amine in most cases. Lithium aluminium hydride reductions of the above imines (3a–e), (1b), and (3f–g), however, showed cis-stereoselectivity; the imines (3a–b) and (1b) afforded only the cis-amines under these conditions. Sodium borohydride reductions of the imines (3a–g) gave conflicting results, the imines (3a–b) and (3f–g) furnishing stereoselectively the trans-amines. Metal–ammonia reductions of the imines (3a–b) and (3f), having a carbocyclic B ring, gave a stereoisomeric mixture of amines; similar reduction of the imines (3c–d) with an oxygen atom in ring B, provided, interestingly, the corresponding trans-amines as the predominant product (84–94%). Reasons for the different stereochemical results observed in the reductions of the imines (3a–g) with various reducing agents have been briefly discussed. The stereochemical assignments of the amines (14)–(15) and (16)–(17) were secured from their 1H and 13C n.m.r. spectra, and also from 1H n.m.r. spectra of their N-acetyl derivatives.

AN EFFICIENT PROCEDURE FOR THE PREPARATION OF A CLASS OF α-CARBOXY-Γ-LACTONES, AND STUDIES ON THEIR TRANSFORMATION TO α-METHYLENE DERIVATIVES

Etude de la reaction du diethoxycarbonylmethanure avec le bromo-3 isochromannol-4, le bromo-4 tetrahydro-2,3,4,5 benzooxepinne-1ol-5, le bromo-2 tetrahydro-1,2,3,4 naphtol-1 et le bromo-6 tetrahydro-6,7,8,9 benzocycloheptenol-5