NOVELTY - Production (M1) of a diazoalkane involves: reacting a N-alkyl-N-nitroso compound with a base and a phase transfer catalyst, without organic solvent.    USE - For production of a diazoalkane (claimed) which is used as intermediates or reactants in reactions such as the etherification of NH bonds, OH bonds or acid bonds, or during syntheses of heterocyclic compounds; in addition and insertion reactions under mild conditions; in chemical syntheses; as methylating agent for a wide variety of compounds, as well as being used for ring expansion or chain extension of ketones and for the conversion of ketones to epoxides; in cloaddition reactions with olefins to produce cyclopropyl or nitrogen-containing heterocyclic rings; in pharmaceutical implications e.g. in the formation of viral protease inhibitors including those to combat HIV, especially where an addition of a carbon atom is required without compromising the chirality of the amino acid or affecting the rest of the molecule; for forming tert-butyl(S)-4-chloro-3-oxo-1-phenylbutan-2-ylcarbamate (Boc-CK) as intermediate for the production of HIV protease inhibitors such as atazanavir or fosamprenavir.    ADVANTAGE - The method produces diazoalkane at a yield of above 75%, preferably approximately 90%. The yield of the N-alkyl-N-nitroso compound is approximately 80%. The N-alkyl-N-nitroso compound separates from the reaction mixture as a discrete phase; can be separated from the reaction mixture without the use of an organic solvent. There is no need for purification of the N-alkyl-N-nitroso compound after it has been recovered. The method (M1)-(M2) produces product which is not purified before use in the method (M2). The method is environmentally friendly. The method does not uses organic solvents to separate the reaction products after the reaction and no purification steps are necessary. The elimination of the need for organic solvent not only reduces the cost of the method compared to those of the prior art, but also has advantageous environmental and waste disposal implications.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) production (M2) of a N-alkyl-N-nitroso compound from a starting material of R2-C(R1)=C(R3)-C(O)-CH)R4)-R5 (II) involving use of a tribasic acid to acidify an amine; and    (2) formation (M3) of the diazoalkane from a starting material involving using the method (M1) and (M2).    R1-R4=H, alkyl, alkenyl, alkoxy, alkoxylate, alkyloxy, alkenyloxy or alkoxyalkyl;    R5=OR7, NR7 or R7;    R7=H or alkyl.